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>

using namespace std;

const int rgb[8][3] = {{0, 0, 0},
                       {0, 0, 255},
                       {0, 255, 0},
                       {0, 255, 255},
                       {255, 0, 0},
                       {255, 0, 255},
                       {255, 255, 0},
                       {255, 255, 255}};
const string name[8] = {"black", "blue", "lime",
                        "aqua", "red", "fuchsia",
                        "yellow", "white"};

int to_decimal(string s) 
{
    int d[2];
    int ret = 0;

    for (int i = 0; i < 2; i++) {
        if ('a' <= s[i] && s[i] <= 'f') 
            d[i] = s[i] - 'a' + 10;
        else
            d[i] = s[i] - '0';
    }

    return d[0] * 16 + d[1];
}

int main()
{
    string inp;

    while (cin >> inp, inp != "0") {
        int r, g, b;
        int d = 200000;
        int idx = 0;
        
        r = to_decimal(inp.substr(1, 2));
        g = to_decimal(inp.substr(3, 2));
        b = to_decimal(inp.substr(5, 2));

        for (int i = 0; i < 8; i++) {
            int tmp;
            tmp = (r - rgb[i][0]) * (r - rgb[i][0]) + 
                (g - rgb[i][1]) * (g - rgb[i][1]) +
                (b - rgb[i][2]) * (b - rgb[i][2]);

            if (tmp < d) {
                d = tmp;
                idx = i;
            }
        }
        cout << name[idx] << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
  
// #define int long long
#define pb push_back
#define print(Target) cout << Target << '\n'

#define REP(i, n) for (int i = 0; i < (n); i++)
#define REPS(i, a, n) for (int i = (a); i < (n); i++)

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vector<int> > vii;
typedef pair<int, int> pii;

bool is_uruu(int y) {return (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0));}

struct COL{
  int n;
  string name;
};

const int c[8][3] = {{0, 0, 0}, {0, 0, 0xff}, {0, 0xff, 0}, {0, 0xff, 0xff}, {0xff, 0, 0}, {0xff, 0, 0xff}, {0xff, 0xff, 0}, {0xff, 0xff, 0xff}};

const string s[8] = {"black", "blue", "lime", "aqua", "red", "fuchsia", "yellow", "white"};

bool cmp(COL lhs, COL rhs)
{
  return (lhs.n < rhs.n);
}

signed main()
{
  //ios::sync_with_stdio(false);
  char sr[2], sg[2], sb[2];
  char sh;
  COL col[8];
  
  while (scanf("%1s", &sh), sh != '0'){
    scanf("%2s%2s%2s", sr, sg, sb);
    int r = strtol(sr, NULL, 16),
        g = strtol(sg, NULL, 16),
        b = strtol(sb, NULL, 16);

    REP(i, 8){
      col[i].n = sqrt((c[i][0] - r) * (c[i][0] - r) + (c[i][1] - g) * (c[i][1] - g) + (c[i][2] - b) * (c[i][2] - b));
      col[i].name = s[i];
    }

    sort(col, col + 8, cmp);
    print(col[0].name);
  }

  return (0);
}

C++: #include <bits/stdc++.h>

using namespace std;

const int RGB[8][3] = {
	{ 0   ,0   ,0   },
	{ 0   ,0   ,255 },
	{ 0   ,255 ,0   },
	{ 0   ,255 ,255 },
	{ 255 ,0   ,0   },
	{ 255 ,0   ,255 },
	{ 255 ,255 ,0   },
	{ 255 ,255 ,255 },
};

const string COLOR[8] = {
	"black",
	"blue",
	"lime",
	"aqua",
	"red",
	"fuchsia",
	"yellow",
	"white",
};

int main() {
	int len, d, j, minD, index;
	int rgb[3];
	string colorInfo, tmp;
	stringstream ss;

	while (cin >> colorInfo, colorInfo[0] == '#') {
		len = colorInfo.size() - 1;

		for (int i = 1, j = 0; i < len; i += 2) {
			ss.clear();
			ss.str("");

			ss << colorInfo[i] << colorInfo[i + 1];
			ss >> tmp;
			//cout << tmp << endl;
			rgb[j++] = strtol(tmp.c_str(), 0, 16);
		}

		minD = INT_MAX;
		for (j = 0; j < 8; j++) {
			d = pow(rgb[0] - RGB[j][0], 2) + pow(rgb[1] - RGB[j][1], 2) + pow(rgb[2] - RGB[j][2], 2);
			if (d < minD) {
				minD = d;
				index = j;
			}
		}

		cout << COLOR[index] << endl;

	}

	return 0;
}

C++: #include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
const int ff=255;
int conv(char *str){
    int ret=0;
    for(int i=0;i<2;i++){
        int val;
        if(str[i]>='0'&&str[i]<='9')val=str[i]-'0';
        else val=str[i]-'a'+10;
        ret=(ret<<4)+val;
    }
    return ret;
}
int main(){
    char *Name[8]={"black","blue","lime","aqua","red","fuchsia","yellow","white"};
    int rgb[3][8]={{0,0,0,0,ff,ff,ff,ff},{0,0,ff,ff,0,0,ff,ff},{0,ff,0,ff,0,ff,0,ff}};
    char str[100];
    while(scanf("%s",str),str[0]!='0'){
        int rgb_[3];
        for(int i=0;i<3;i++){
            rgb_[i]=conv(str+1+i*2);
        }
        int mav,mac=1e9;
        for(int i=0;i<8;i++){
            int val=0;
            for(int j=0;j<3;j++)val+=(rgb_[j]-rgb[j][i])*(rgb_[j]-rgb[j][i]);
            if(mac>val){
                mac=val;
                mav=i;
            }
        }
        printf("%s\n",Name[mav]);

    }
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

string colors[] = {"black", "blue", "lime", "aqua", "red", "fuchsia", "yellow", "white"};

int dis(int id, vector<int> a){
  int res = 0;
  for(int i=0;i<3;i++){
    int comp = 0;
    if(id&1) comp = 255;
    res += (a[i]-comp)*(a[i]-comp);
    id/=2;
  }
  return res;
}

int toDec(char a){
  if(isdigit(a))return a-'0';
  return a-'a'+10;
}

int main(){
  string s;
  while(cin >> s, s != "0"){
    vector<int> a(3);
    for(int i=0;i<3;i++){
      a[i] = toDec(s[2*i+1])*16 + toDec(s[2*i+2]);
    }
    reverse(a.begin(), a.end());
    int ans = 0, dmin = dis(0,a);
    for(int i=1;i<8;i++){
      if(dis(i,a) < dmin){
        ans = i; dmin = dis(i,a);
      }
    }
    cout << colors[ans] << endl;
  }
}

C++: #include<iostream>
#include<string>
#include<cstring>
#include<cctype>
#include<cmath>
#define loop(i,a,b) for(int i=a;i<b;i++)
#define rep(i,a) loop(i,0,a)
#define INF 1e6
using namespace std;

int d(string s,int color[3]){
  int red=0,blue=0,green=0;
  if(!isdigit(s[1]))red+=(s[1]-'a'+10)*16;
  else red+=(s[1]-'0')*16;
  if(!isdigit(s[2]))red+=(s[2]-'a'+10);
  else red+=(s[2]-'0');
  if(!isdigit(s[3]))green+=(s[3]-'a'+10)*16;
  else green+=(s[3]-'0')*16;
  if(!isdigit(s[4]))green+=(s[4]-'a'+10);
  else green+=(s[4]-'0');
  if(!isdigit(s[5]))blue+=(s[5]-'a'+10)*16;
  else blue+=(s[5]-'0')*16;
  if(!isdigit(s[6]))blue+=(s[6]-'a'+10);
  else blue+=(s[6]-'0');   
  return sqrt(pow((red-color[0]),2)+pow((green-color[1]),2)+pow((blue-color[2]),2));
}

int cl[8][3]={{0,0,0},{0,0,255},{0,255,0},{0,255,255},{255,0,0},{255,0,255},{255,255,0},{255,255,255}};

int main(){
  string str;
  while(1){
    cin>>str;
    if(str=="0")break;
    int num=INF;
    string ans="";
    rep(i,8){
      if(num>d(str,cl[i])){
	if(i==0)ans="black";
	else if(i==1)ans="blue";
	else if(i==2)ans="lime";
	else if(i==3)ans="aqua";
	else if(i==4)ans="red";
	else if(i==5)ans="fuchsia";
	else if(i==6)ans="yellow";
	else if(i==7)ans="white";
	num=d(str,cl[i]);
      }
    }
    cout<<ans<<endl;
  }
  return 0;
}