Below is a master list of all possible string arguments for system.gui.color() assigned to a variable for use in scripting functions. I originally created this for the random confetti generator I developed for BANANAS Version 2, but it's been coming in quite handy elsewhere, so I'm posting it here:
possibleStringColors = [
#String, #Hex #RGB
'AliceBlue', # #F0F8FF (240, 248, 255)
'AntiqueWhite', # #FAEBD7 (250, 235, 215)
'Aqua', # #00FFFF (0, 255, 255)
'Aquamarine', # #7FFFD4 (127, 255, 212)
'Azure', # #F0FFFF (240, 255, 255)
'Beige', # #F5F5DC (245, 245, 220)
'Bisque', # #FFE4C4 (255, 228, 196)
'Black', # #000000 (0, 0, 0)
'BlanchedAlmond', # #FFEBCD (255, 235, 205)
'Blue', # #0000FF (0, 0, 255)
'BlueViolet', # #8A2BE2 (138, 43, 226)
'Brown', # #A52A2A (165, 42, 42)
'BurlyWood', # #DEB887 (222, 184, 135)
'CadetBlue', # #5F9EA0 (95, 158, 160)
'Chartreuse', # #7FFF00 (127, 255, 0)
'Chocolate', # #D2691E (210, 105, 30)
'Clear', # #FFFFFF (255, 255, 255, 0)
'Coral', # #FF7F50 (255, 127, 80)
'CornflowerBlue', # #6495ED (100, 149, 237)
'Cornsilk', # #FFF8DC (255, 248, 220)
'Crimson', # #DC143C (220, 20, 60)
'Cyan', # #00FFFF (0, 255, 255)
'DarkBlue', # #00008B (0, 0, 139)
'DarkCyan', # #008B8B (0, 139, 139)
'DarkGoldenRod', # #B8860B (184, 134, 11)
'DarkGrey', # #A9A9A9 (169, 169, 169)
'DarkGreen', # #006400 (0, 100, 0)
'DarkKhaki', # #BDB76B (189, 183, 107)
'DarkMagenta', # #8B008B (139, 0, 139)
'DarkOliveGreen', # #556B2F (85, 107, 47)
'Darkorange', # #FF8C00 (255, 140, 0)
'DarkOrchid', # #9932CC (153, 50, 204)
'DarkRed', # #8B0000 (139, 0, 0)
'DarkSalmon', # #E9967A (233, 150, 122)
'DarkSeaGreen', # #8FBC8F (143, 188, 143)
'DarkSlateBlue', # #483D8B (72, 61, 139)
'DarkSlateGrey', # #2F4F4F (47, 79, 79)
'DarkTurquoise', # #00CED1 (0, 206, 209)
'DarkViolet', # #9400D3 (148, 0, 211)
'DeepPink', # #FF1493 (255, 20, 147)
'DeepSkyBlue', # #00BFFF (0, 191, 255)
'DimGrey', # #696969 (105, 105, 105)
'DodgerBlue', # #1E90FF (30, 144, 255)
'Feldspar', # #D19275 (209, 146, 117)
'FireBrick', # #B22222 (178, 34, 34)
'FloralWhite', # #FFFAF0 (255, 250, 240)
'ForestGreen', # #228B22 (34, 139, 34)
'Fuchsia', # #FF00FF (255, 0, 255)
'Gainsboro', # #DCDCDC (220, 220, 220)
'GhostWhite', # #F8F8FF (248, 248, 255)
'Gold', # #FFD700 (255, 215, 0)
'GoldenRod', # #DAA520 (218, 165, 32)
'Grey', # #808080 (128, 128, 128)
'Green', # #008000 (0, 128, 0)
'GreenYellow', # #ADFF2F (173, 255, 47)
'HoneyDew', # #F0FFF0 (240, 255, 240)
'HotPink', # #FF69B4 (255, 105, 180)
'IndianRed', # #CD5C5C (205, 92, 92)
'Indigo', # #4B0082 (75, 0, 130)
'Ivory', # #FFFFF0 (255, 255, 240)
'Khaki', # #F0E68C (240, 230, 140)
'Lavender', # #E6E6FA (230, 230, 250)
'LavenderBlush', # #FFF0F5 (255, 240, 245)
'LawnGreen', # #7CFC00 (124, 252, 0)
'LemonChiffon', # #FFFACD (255, 250, 205)
'LightBlue', # #ADD8E6 (173, 216, 230)
'LightCoral', # #F08080 (240, 128, 128)
'LightCyan', # #E0FFFF (224, 255, 255)
'LightGoldenRodYellow', # #FAFAD2 (250, 250, 210)
'LightGreen', # #90EE90 (144, 238, 144)
'LightGrey', # #D3D3D3 (211, 211, 211)
'LightPink', # #FFB6C1 (255, 182, 193)
'LightSalmon', # #FFA07A (255, 160, 122)
'LightSeaGreen', # #20B2AA (32, 178, 170)
'LightSkyBlue', # #87CEFA (135, 206, 250)
'LightSlateBlue', # #8470FF (132, 112, 255)
'LightSlateGrey', # #778899 (119, 136, 153)
'LightSteelBlue', # #B0C4DE (176, 196, 222)
'LightYellow', # #FFFFE0 (255, 255, 224)
'Lime', # #00FF00 (0, 255, 0)
'LimeGreen', # #32CD32 (50, 205, 50)
'Linen', # #FAF0E6 (250, 240, 230)
'Magenta', # #FF00FF (255, 0, 255)
'Maroon', # #800000 (128, 0, 0)
'MediumAquaMarine', # #66CDAA (102, 205, 170)
'MediumBlue', # #0000CD (0, 0, 205)
'MediumOrchid', # #BA55D3 (186, 85, 211)
'MediumPurple', # #9370DB (147, 112, 219)
'MediumSeaGreen', # #3CB371 (60, 179, 113)
'MediumSlateBlue', # #7B68EE (123, 104, 238)
'MediumSpringGreen', # #00FA9A (0, 250, 154)
'MediumTurquoise', # #48D1CC (72, 209, 204)
'MediumVioletRed', # #C71585 (199, 21, 133)
'MidnightBlue', # #191970 (25, 25, 112)
'MintCream', # #F5FFFA (245, 255, 250)
'MistyRose', # #FFE4E1 (255, 228, 225)
'Moccasin', # #FFE4B5 (255, 228, 181)
'NavajoWhite', # #FFDEAD (255, 222, 173)
'Navy', # #000080 (0, 0, 128)
'OldLace', # #FDF5E6 (253, 245, 230)
'Olive', # #808000 (128, 128, 0)
'OliveDrab', # #6B8E23 (107, 142, 35)
'Orange', # #FFA500 (255, 165, 0)
'OrangeRed', # #FF4500 (255, 69, 0)
'Orchid', # #DA70D6 (218, 112, 214)
'PaleGoldenRod', # #EEE8AA (238, 232, 170)
'PaleGreen', # #98FB98 (152, 251, 152)
'PaleTurquoise', # #AFEEEE (175, 238, 238)
'PaleVioletRed', # #DB7093 (219, 112, 147)
'PapayaWhip', # #FFEFD5 (255, 239, 213)
'PeachPuff', # #FFDAB9 (255, 218, 185)
'Peru', # #CD853F (205, 133, 63)
'Pink', # #FFC0CB (255, 192, 203)
'Plum', # #DDA0DD (221, 160, 221)
'PowderBlue', # #B0E0E6 (176, 224, 230)
'Purple', # #800080 (128, 0, 128)
'Red', # #FF0000 (255, 0, 0)
'RosyBrown', # #BC8F8F (188, 143, 143)
'RoyalBlue', # #4169E1 (65, 105, 225)
'SaddleBrown', # #8B4513 (139, 69, 19)
'Salmon', # #FA8072 (250, 128, 114)
'SandyBrown', # #F4A460 (244, 164, 96)
'SeaGreen', # #2E8B57 (46, 139, 87)
'SeaShell', # #FFF5EE (255, 245, 238)
'Sienna', # #A0522D (160, 82, 45)
'Silver', # #C0C0C0 (192, 192, 192)
'SkyBlue', # #87CEEB (135, 206, 235)
'SlateBlue', # #6A5ACD (106, 90, 205)
'SlateGrey', # #708090 (112, 128, 144)
'Snow', # #FFFAFA (255, 250, 250)
'SpringGreen', # #00FF7F (0, 255, 127)
'SteelBlue', # #4682B4 (70, 130, 180)
'Tan', # #D2B48C (210, 180, 140)
'Teal', # #008080 (0, 128, 128)
'Thistle', # #D8BFD8 (216, 191, 216)
'Tomato', # #FF6347 (255, 99, 71)
'Transparent', # #FFFFFF (255, 255, 255, 0)
'Turquoise', # #40E0D0 (64, 224, 208)
'Violet', # #EE82EE (238, 130, 238)
'VioletRed', # #D02090 (208, 32, 144)
'Wheat', # #F5DEB3 (245, 222, 179)
'White', # #FFFFFF (255, 255, 255)
'WhiteSmoke', # #F5F5F5 (245, 245, 245)
'Yellow', # #FFFF00 (255, 255, 0)
'YellowGreen' # #9ACD32 (154, 205, 50)
]