This is an extension to the problem Can you code 1/1/2/2/3/3

Start with 10 blue balls and 10 red balls and create the pattern

rrrrBBBBrrrBBBrrBBrB

i.e. 1 of each colour, then 2 of each, then 3, then 4

Standard set of parts on the standard sized board.

I wasn’t sure at first if this were possible. I spent a couple of hours on it and was just about to give up when I tried one more possibility and it came together. The solution has a pleasing mirror symmetry.