rgb to console color
int index = (c.R > 128 | c.G > 128 | c.B > 128) ? 8 : 0;
index |= (c.R > 64) ? 4 : 0;
index |= (c.G > 64) ? 2 : 0;
index |= (c.B > 64) ? 1 : 0;
Console.ForegroundColor = (System.ConsoleColor)index;