GUI Improvement: Troops filter dialog.
Instead of showing 1 gem like now, with left right arrows, show all gems, including the 6 colored gem, next to one another.
Now all you need is a highlight effect for selected gems, for example not selected are dimmed, selected are bright.
Only 6 colored gem selected (default): Show all troops
Only 1 of the 6 normal gem colors selected: Show all troops with only that color.
2 of the 6 normal gem colors selected: Show all troops with those 2 colors.
3 of the 6 normal gem colors selected: Show all troops with those 3 colors.
etc.
1 normal gem color + 6 colored gem selected: Show all troops that contain at least that 1 gem color (so same as current gem filter).
2 normal gem colors + 6 colored gem selected: Show all troops that contain at least those 2 gem colors.