Python, finding nearest matching color name for RGB values

There are 147 standard color names for use in HTML. here is a simple Python code to find the nearest matching color name given input R,G, B values (from 0-255). The minimization criterion is the sum of absolute vaues of the differences from the color r, g, b values of the colornames.

"""
File    colornames.py
Author  Ernesto P. Adorio, Ph.D
Version 0.0.1 February 1, 2012
"""


# Src: http://www.w3schools.com/html/html_colornames.asp
lines = """AliceBlue  #F0F8FF   Shades Mix
AntiqueWhite  #FAEBD7   Shades Mix
Aqua  #00FFFF   Shades Mix
Aquamarine  #7FFFD4   Shades Mix
Azure  #F0FFFF   Shades Mix
Beige  #F5F5DC   Shades Mix
Bisque  #FFE4C4   Shades Mix
Black  #000000   Shades Mix
BlanchedAlmond  #FFEBCD   Shades Mix
Blue  #0000FF   Shades Mix
BlueViolet  #8A2BE2   Shades Mix
Brown  #A52A2A   Shades Mix
BurlyWood  #DEB887   Shades Mix
CadetBlue  #5F9EA0   Shades Mix
Chartreuse  #7FFF00   Shades Mix
Chocolate  #D2691E   Shades Mix
Coral  #FF7F50   Shades Mix
CornflowerBlue  #6495ED   Shades Mix
Cornsilk  #FFF8DC   Shades Mix
Crimson  #DC143C   Shades Mix
Cyan  #00FFFF   Shades Mix
DarkBlue  #00008B   Shades Mix
DarkCyan  #008B8B   Shades Mix
DarkGoldenRod  #B8860B   Shades Mix
DarkGray  #A9A9A9   Shades Mix
DarkGrey  #A9A9A9   Shades Mix
DarkGreen  #006400   Shades Mix
DarkKhaki  #BDB76B   Shades Mix
DarkMagenta  #8B008B   Shades Mix
DarkOliveGreen  #556B2F   Shades Mix
Darkorange  #FF8C00   Shades Mix
DarkOrchid  #9932CC   Shades Mix
DarkRed  #8B0000   Shades Mix
DarkSalmon  #E9967A   Shades Mix
DarkSeaGreen  #8FBC8F   Shades Mix
DarkSlateBlue  #483D8B   Shades Mix
DarkSlateGray  #2F4F4F   Shades Mix
DarkSlateGrey  #2F4F4F   Shades Mix
DarkTurquoise  #00CED1   Shades Mix
DarkViolet  #9400D3   Shades Mix
DeepPink  #FF1493   Shades Mix
DeepSkyBlue  #00BFFF   Shades Mix
DimGray  #696969   Shades Mix
DimGrey  #696969   Shades Mix
DodgerBlue  #1E90FF   Shades Mix
FireBrick  #B22222   Shades Mix
FloralWhite  #FFFAF0   Shades Mix
ForestGreen  #228B22   Shades Mix
Fuchsia  #FF00FF   Shades Mix
Gainsboro  #DCDCDC   Shades Mix
GhostWhite  #F8F8FF   Shades Mix
Gold  #FFD700   Shades Mix
GoldenRod  #DAA520   Shades Mix
Gray  #808080   Shades Mix
Grey  #808080   Shades Mix
Green  #008000   Shades Mix
GreenYellow  #ADFF2F   Shades Mix
HoneyDew  #F0FFF0   Shades Mix
HotPink  #FF69B4   Shades Mix
IndianRed   #CD5C5C   Shades Mix
Indigo   #4B0082   Shades Mix
Ivory  #FFFFF0   Shades Mix
Khaki  #F0E68C   Shades Mix
Lavender  #E6E6FA   Shades Mix
LavenderBlush  #FFF0F5   Shades Mix
LawnGreen  #7CFC00   Shades Mix
LemonChiffon  #FFFACD   Shades Mix
LightBlue  #ADD8E6   Shades Mix
LightCoral  #F08080   Shades Mix
LightCyan  #E0FFFF   Shades Mix
LightGoldenRodYellow  #FAFAD2   Shades Mix
LightGray  #D3D3D3   Shades Mix
LightGrey  #D3D3D3   Shades Mix
LightGreen  #90EE90   Shades Mix
LightPink  #FFB6C1   Shades Mix
LightSalmon  #FFA07A   Shades Mix
LightSeaGreen  #20B2AA   Shades Mix
LightSkyBlue  #87CEFA   Shades Mix
LightSlateGray  #778899   Shades Mix
LightSlateGrey  #778899   Shades Mix
LightSteelBlue  #B0C4DE   Shades Mix
LightYellow  #FFFFE0   Shades Mix
Lime  #00FF00   Shades Mix
LimeGreen  #32CD32   Shades Mix
Linen  #FAF0E6   Shades Mix
Magenta  #FF00FF   Shades Mix
Maroon  #800000   Shades Mix
MediumAquaMarine  #66CDAA   Shades Mix
MediumBlue  #0000CD   Shades Mix
MediumOrchid  #BA55D3   Shades Mix
MediumPurple  #9370D8   Shades Mix
MediumSeaGreen  #3CB371   Shades Mix
MediumSlateBlue  #7B68EE   Shades Mix
MediumSpringGreen  #00FA9A   Shades Mix
MediumTurquoise  #48D1CC   Shades Mix
MediumVioletRed  #C71585   Shades Mix
MidnightBlue  #191970   Shades Mix
MintCream  #F5FFFA   Shades Mix
MistyRose  #FFE4E1   Shades Mix
Moccasin  #FFE4B5   Shades Mix
NavajoWhite  #FFDEAD   Shades Mix
Navy  #000080   Shades Mix
OldLace  #FDF5E6   Shades Mix
Olive  #808000   Shades Mix
OliveDrab  #6B8E23   Shades Mix
Orange  #FFA500   Shades Mix
OrangeRed  #FF4500   Shades Mix
Orchid  #DA70D6   Shades Mix
PaleGoldenRod  #EEE8AA   Shades Mix
PaleGreen  #98FB98   Shades Mix
PaleTurquoise  #AFEEEE   Shades Mix
PaleVioletRed  #D87093   Shades Mix
PapayaWhip  #FFEFD5   Shades Mix
PeachPuff  #FFDAB9   Shades Mix
Peru  #CD853F   Shades Mix
Pink  #FFC0CB   Shades Mix
Plum  #DDA0DD   Shades Mix
PowderBlue  #B0E0E6   Shades Mix
Purple  #800080   Shades Mix
Red  #FF0000   Shades Mix
RosyBrown  #BC8F8F   Shades Mix
RoyalBlue  #4169E1   Shades Mix
SaddleBrown  #8B4513   Shades Mix
Salmon  #FA8072   Shades Mix
SandyBrown  #F4A460   Shades Mix
SeaGreen  #2E8B57   Shades Mix
SeaShell  #FFF5EE   Shades Mix
Sienna  #A0522D   Shades Mix
Silver  #C0C0C0   Shades Mix
SkyBlue  #87CEEB   Shades Mix
SlateBlue  #6A5ACD   Shades Mix
SlateGray  #708090   Shades Mix
SlateGrey  #708090   Shades Mix
Snow  #FFFAFA   Shades Mix
SpringGreen  #00FF7F   Shades Mix
SteelBlue  #4682B4   Shades Mix
Tan  #D2B48C   Shades Mix
Teal  #008080   Shades Mix
Thistle  #D8BFD8   Shades Mix
Tomato  #FF6347   Shades Mix
Turquoise  #40E0D0   Shades Mix
Violet  #EE82EE   Shades Mix
Wheat  #F5DEB3   Shades Mix
White  #FFFFFF   Shades Mix
WhiteSmoke  #F5F5F5   Shades Mix
Yellow  #FFFF00   Shades Mix
YellowGreen  #9ACD32"""

def rgbfromstr(s):
    # s starts with a #.
    r, g, b = int(s[1:3],16), int(s[3:5], 16),int(s[5:7], 16)
    return r, g, b

def findnearestcolorname(R,G, B, colorD):
    mindiff = None

    for d in colorD:
       r, g, b = rgbfromstr(colorD[d])
       diff = abs(R -r)*256 + abs(G-g)* 256 + abs(B- b)* 256 
       if mindiff is None or diff < mindiff:
          mindiff = diff
          mincolorname = d
    return mincolorname
 

if __name__ == "__main__":
  D={}
  for line in lines.split("\n"):
    tokens = line.split()
    if len(tokens) > 1:
        D[tokens[0]]= tokens[1]
     
  R, G, B = 0, 127, 127
  colorname = findnearestcolorname(0, 127, 127, D)
  print hex(R), hex(G), hex(B)
  print colorname, D[colorname]
 

When the above program runs, it outputs


$ python colornames.py
0x0 0x7f 0x7f
Teal #008080



Questions.

1. Modify the minimizaiton criterion to use least sum of squares of the differences.

2. Provide error checking for input R, G, B values to be within the interval [0, 255].

3. Procide different ways to specify the input RGB values, aside from the (R, G, B) values as done in the program above.