func ColorRGB(r, g, b int) Attribute {
	within := func(n int) int {
		if n < 0 {
			return 0
		}
		if n > 5 {
			return 5
		}
		return n
	}
	r, b, g = within(r), within(b), within(g)
	return Attribute(0x0f + 36*r + 6*g + b)
}
0<=r,g,b <= 5
package termui
import "strings"
var ColorMap = map[string]Attribute{
	"fg":           ColorWhite,
	"bg":           ColorDefault,
	"border.fg":    ColorWhite,
	"label.fg":     ColorGreen,
	"par.fg":       ColorYellow,
	"par.label.bg": ColorWhite,
}
func ThemeAttr(name string) Attribute {
	return lookUpAttr(ColorMap, name)
}
func lookUpAttr(clrmap map[string]Attribute, name string) Attribute {
	a, ok := clrmap[name]
	if ok {
		return a
	}
	ns := strings.Split(name, ".")
	for i := range ns {
		nn := strings.Join(ns[i:len(ns)], ".")
		a, ok = ColorMap[nn]
		if ok {
			break
		}
	}
	return a
}