Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

type Color struct {
	name    string
	R, G, B int64
}

func main() {
	colors := []Color{
		{"black", 0, 0, 0},
		{"blue", 0, 0, 0xff},
		{"lime", 0, 0xff, 0},
		{"aqua", 0, 0xff, 0xff},
		{"red", 0xff, 0, 0},
		{"fuchsia", 0xff, 0, 0xff},
		{"yellow", 0xff, 0xff, 0},
		{"white", 0xff, 0xff, 0xff},
	}
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), "")
		if buf[0] == "0" {
			break
		}
		r, _ := strconv.ParseInt(strings.Join(buf[1:3], ""), 16, 64)
		g, _ := strconv.ParseInt(strings.Join(buf[3:5], ""), 16, 64)
		b, _ := strconv.ParseInt(strings.Join(buf[5:], ""), 16, 64)
		vmin := int64(3*0xff*0xff)
		var ans string
		for _, c := range colors {
			d := (r-c.R)*(r-c.R) + (g-c.G)*(g-c.G) + (b-c.B)*(b-c.B)
			if d < vmin {
				vmin = d
				ans = c.name
			}
		}
		fmt.Println(ans)
	}
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <cstring>
#include <string>
#include <sstream>
#include <algorithm>
#include <iomanip>
using namespace std;

const int INF = 1e9;
typedef long long ll;

struct Color{
  string name;
  int R, G, B;
};

Color list[8];

void init(){
  list[0].name = "black";   list[0].R = 0x00; list[0].G = 0x00; list[0].B = 0x00;
  list[1].name = "blue";    list[1].R = 0x00; list[1].G = 0x00; list[1].B = 0xff;
  list[2].name = "lime";    list[2].R = 0x00; list[2].G = 0xff; list[2].B = 0x00;
  list[3].name = "aqua";    list[3].R = 0x00; list[3].G = 0xff; list[3].B = 0xff;
  list[4].name = "red";     list[4].R = 0xff; list[4].G = 0x00; list[4].B = 0x00;
  list[5].name = "fuchsia"; list[5].R = 0xff; list[5].G = 0x00; list[5].B = 0xff;
  list[6].name = "yellow";  list[6].R = 0xff; list[6].G = 0xff; list[6].B = 0x00;
  list[7].name = "white";   list[7].R = 0xff; list[7].G = 0xff; list[7].B = 0xff;
}

int main(void){
  init();
  string colorcode;
  while(cin >> colorcode && colorcode != "0"){
    int r = stoi(string(colorcode, 1, 2), nullptr, 16);
    int g = stoi(string(colorcode, 3, 2), nullptr, 16);
    int b = stoi(string(colorcode, 5, 2), nullptr, 16);
    int n, mind = INF;
    for(int i = 0; i < 8; i++){
      int d = (r - list[i].R) * (r - list[i].R) + (g - list[i].G) * (g - list[i].G) + (b - list[i].B) * (b - list[i].B);
      if(d < mind){
        mind = d;
        n = i;
      }
    }
    cout << list[n].name << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cmath>

using namespace std;

typedef vector<int> vi;
typedef vector<vi> vii;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<vb> vbb;
typedef pair<int, int> pii;
typedef long long ll;
typedef unsigned long long ull;

#define all(a)  (a).begin(),(a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define pb push_back
#define mp make_pair

#define loop(i,a,b) for(int i=(a);i<ull(b);++i)
#define rep(i,n) loop(i,0,n)

const double eps = 1e-10;
const double pi  = acos(-1.0);
const double inf = (int)1e8;

string color[8] = {"black", "blue", "lime", "aqua", "red", "fuchsia", "yellow", "white"};
string strength[8] = {"000000", "0000ff", "00ff00", "00ffff", "ff0000", "ff00ff", "ffff00", "ffffff"};

int toi(string s){
    int ret = 0;
    rep(i, s.size()){
        string t = s.substr(i, 1);
        if('0' <= t[0] && t[0] <= '9') ret += stoi(t);
        else ret += t[0]-'a'+10;
        if(i != s.size()-1) ret *= 16;
    }
    return ret;
}

vector<int> rgb(string s){
    vi ret;
    rep(i, 3){
        string t = s.substr(i*2, 2);
        ret.pb(toi(t));
    }
    return ret;
}

int main(){
    string  s;
    while(cin >> s, s!="0"){
        s = s.substr(1);
        vi c = rgb(s);
        int m = inf;
        int ans = 0;
        rep(i, 8){
            vi d = rgb(strength[i]);
            int ret = sqrt(pow(c[0]-d[0], 2)+pow(c[1]-d[1], 2)+pow(c[2]-d[2], 2));
            if(m > ret){ans = i; m = ret;}
        }
        cout << color[ans] << endl;
    }
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<map>
#include<cstring>
using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define REP(n) rep(i,n)
#define all(n) n.begin(),n.end()

const int FF = 255;

string name[] = {"black", "blue", "lime", "aqua", "red", "fuchsia", "yellow", "while"};
int R[] = { 0, 0, 0, 0, FF, FF, FF, FF};
int G[] = { 0, 0, FF, FF, 0, 0, FF, FF};
int B[] = { 0, FF, 0, FF, 0, FF, 0, FF};

int num(char t)
{
    if(t >='0' && t <= '9') return t - '0';
    else return t - 'a' + 10;
}
int f(int n) { return n * n;}

int main()
{
    string s;
    while(cin >> s)
    {
        if(s == "0") break;

        int mind = FF * FF * 4, d = 0, ans = 0;
        REP(8)
        {
            d = f(R[i] -( num(s[1]) * 16 + num(s[2]) )) + f(G[i]-(num(s[3])*16+num(s[4]))) + f(B[i] - (num(s[5])*16 + num(s[6])));
            if(mind > d) { ans = i; mind = d;}
        }
        cout << name[ans] << endl;
    }
    return 0;
}

C++: #include <cstdio>
#include <utility>
#include <cctype>
#include <vector>
#include <string>
#include <cfloat>
#include <algorithm>
#include <cmath>
using namespace std;

#ifdef __linux
#define _U(s) s##_unlocked
#else
#define _U(s) _##s##_nolock
#define _CRT_DISABLE_PERFCRIT_LOCKS
#endif
#define gcu _U(getchar)
#define pcu _U(putchar)
#define _DEF(r, n, ...) inline r n(__VA_ARGS__) noexcept
#define _T template <typename T>
#define _HT template <typename H,typename... T>
#define _OP(t) inline operator t()
struct _in {
#ifdef _GLIBCXX_STRING
	_OP(string){string s;for(char c;c=gcu(),c!=' '&&c!='\n'&&c!=EOF;)s+=c;return s;}
#define _S
#endif
	_OP(char){char c=gcu();gcu();return c;}
	_OP(double){double d; scanf("%lf",&d); gcu();return d;}
	_T _OP(T){T n{},m{1},c;while(isspace(c = gcu()));if(c=='-')m=-1,c=gcu();do{n=10*n+(c-'0'),c=gcu();}while(c>='0'&&c<='9');return m*n;}
} in;
#define _SCAN(...) _DEF(bool,scan,__VA_ARGS__)
#ifdef _S
_SCAN(string &o) {int c{gcu()};if(c==EOF)return false;else{ungetc(c,stdin);string t=move(in);o=t;return true;}}
#endif
_T _SCAN(T &o) {int c{gcu()};return c==EOF?false:(ungetc(c,stdin),o=in,true);}
_HT _SCAN(H &h,T&&... t){return scan(h)&&scan(t...);}
#define _OUT(...) _DEF(void,out,__VA_ARGS__)
#define _OUTL(...) _DEF(void,outl,__VA_ARGS__)
_OUT(bool b){pcu('0'+b);}
_OUT(const char *s){while(*s)pcu(*s++);}
_OUT(char c){pcu(c);}
#ifdef _S
_OUT(string &s){for(char c:s)pcu(c);}
#endif
_T _OUT(T n){static char b[20];char *p=b;T m=n<0?pcu('-'),-1:1;
	if(!n)*p++='0';else while(n)*p++=(char)(n%10*m+'0'),n/=10;while(p!=b)pcu(*--p);}
_OUTL(){out('\n');}
#ifdef _GLIBCXX_VECTOR
	_T _OUT(vector<T> &v){for(T &x:v)out(&x == &v[0]?"":" "),out(x);}
#endif
	_HT _OUT(H &&h, T... t){out(h);out(t...);}
	template <typename... T> _OUTL(T... t){out(t...);outl();}
	struct range{
		int e,b=0,s=1;range(int _b,int _e,int _s):e(_e),b(_b),s(_s){} range(int _b,int _e): e(_e), b(_b){} range(int _e):e(_e){}
		struct it{int v,s; it(int _v,int _s):v(_v),s(_s){} operator int()const{return v;} operator int&(){return v;}int operator*()const{return v;}
			it& operator++(){v+=s;return *this;} }; it begin(){return {b,s};} it end(){return {e,s};}};
#define times(i,n) for(int i=n;i;i--)

struct C {
	int r, g, b;
};

int sq(int n) {
	return n * n;
}

int main() {
	vector<C> t {{0x00, 0x00, 0x00}, {0x00, 0x00, 0xff}, {0x00, 0xff, 0x00}, {0x00, 0xff, 0xff},
		{0xff, 0x00, 0x00}, {0xff, 0x00, 0xff}, {0xff, 0xff, 0x00}, {0xff, 0xff, 0xff}};
	vector<string> S{"black", "blue", "lime", "aqua", "red", "fuchsia", "yellow", "white"};
	for (int r, g, b; scanf("#%2x%2x%2x\n", &r, &g, &b);) {
		double m {DBL_MAX}, i {};
		for (int j: range(t.size())) {
			double s = sqrt(sq(r - t[j].r) + sq(g - t[j].g) + sq(b - t[j].b));
			if (s < m)
				m = s, i = j;
		}
		outl(S[i]);
	}
}