Nice touch! I was preparing to do exactly the same thing!
The steel balls are more in-line with the back-glass art. There are no colored gumballs featured in any of the playfield or back-glass art so far as I can tell (save for the "loose" gumballs depicted on the gumball's plastic apron/ escutcheon). Good eye!
I especially like the icy blue tint you've given the feature. Once again, in keeping with the back-glass art and that overall "icy", cold, appearance - looks great.
Well done in keeping true to the depicted art.
Will post mine after I finish getting everything squared away. I've got a new gumball diverter and pcb setup constructed to replace the OEM part. Now, just bread-boarding different colors / color temp leds to find that perfect effect.