This problem was found in 4.12.3 last year. Bringing it back up because it has not been patched in 4.12.6.
The issue occurs when you make more than one RGB Matrix with the pattern "Vertical fall". When choosing different colors on multiple other "Vertical fall" matrices, the color you choose switches to the first color you gave out of the multiple you made. This can be fixed by resetting the software, but quickly reverts as you execute the functions.