Show the list of available colors for curves

[fa201]

Add a "Show colors" button. It opens a toplevel window showing the liste of available colors and their name.

[fa201]

[
"black",
"red",
"blue",
"green",
"orange",
"yellow",
"magenta",
"cyan",
"olive",
"teal",
"gray",
"white",
"aquamarine",
"blue3",
"burlywood",
"burlywood1",
"chartreuse",
"chocolate1",
"chocolate4",
"crimson",
"DarkGoldenrod3",
"DodgerBlue",
"gold",
"green3",
"indigo",
"khaki1",
"khaki3",
"LightSeaGreen",
"maroon",
"navy",
"OliveDrab1",
"OliveDrab3",
"peru",
"purple1",
"purple3",
"RoyalBlue",
"salmon",
"SeaGreen",
"SlateBlue1",
"SpringGreen",
"SteelBlue",
"tan4",
"turquoise",
"violet",
"VioletRed1",
"gray16",
"gray21",
"gray26",
"gray31",
"gray36",
"gray41",
"gray46",
"gray51",
"gray56",
"gray61",
"gray66",
"gray71",
"gray76",
"gray81",
"gray86",
]