Not willing to pay over the odds for what the rainmakers pack goes for these days (or even when it originally came out since it never hit the UK), I made my own. Honestly, I like the silver chests more than the all solid colour anyway, and never liked the battle damage so that was left off. Ion Storm is just a straight up Thundercracker, with the justification his electrical powers are much more intense than Shrapnel, and cause scorching on his armour as he tries to contain it. Although I may paint his grey chest silver to match, and go over his black bits to remove that battle damage. Acid looks a little darker in the first picture because of the light source, but he's meant to be the lighter green of his alt mode pics.
Another idea is go pick up another Starscream and swap out the blue feet and fore arms, It'll give you a close approximation of Ion Storm and a "Animation Error" Starscream too
I never cared for the solid color of the Rainmakers in robot mode. Really like what you did with the silver in robot mode.