Duplicated Color

[rwxguo]

Current color palette is selected from 8 scopes name. The color may be duplicated in some color schemes. That makes highlighter confusing when each highlight use the same color in file. The issue caused by :

1. Some scopes are not defined
2. Some scopes are defined by the same color

To resolve this problem, it is suggested that when creating "colors_by_scope", do not add all scopes, instead, skip the scopes which color is the same as the scopes already inserted into "colors_by_scope" by comparing the color HEX.

Besides, please add more scopes into "colors_by_scope" to increase the number of highlight avaliable.

[kdnk]

Actually, I haven't been using Sublime Text much lately.
Can you create a PR, if you'd like?