Now that we have 6 distinct colors - Blue, Green, Red, Yellow, Purple, Brown, I have come to a new conclusion. Multicolored Gemstones may be needed.
There should be several known types:
For example: (one gem could consist of two or more gem colors)
Brown/Yellow - Can be matched by Brown or Yellow.
Brown/Yellow/Red - Can be matched by Brown, Yellow or Red.
Super Gem - Multicolored Gem (all 6 colors) - Can be matched by any color to make a match.
etc. - etc.
Special Circumstances: (Limitations - To not make things too unstable or overpowered.)
- Mana surge should not count with such matches.
- Color increase or mana gain should be adjusted accordingly to compensate.
- Such gems should be rare enough in % to make things more interesting, but not broken, etc.