I feel your pain on this one.
In the Rows menu you can use Color or Mark by Column and make an external legend, as well as save the colors to the column property.
HOWEVER!!, even though the color is set for the column, the rings (as well as pretty much every graphical element in the Fit Y by X platform) ignores this, so coloring of boxes, rings, diamonds etc, all has to be done manually, one at a time, for every single graph you make.
At the top of the screen, there is a "Wishlist" link. This might be a good thing to add there, if you have a few moments. (Staff can't add items to this wishlist)
JMP Systems Engineer, Health and Life Sciences (Pharma)