I'd base it on the color of my boat. If you have a dark color hull, I'd go blue. Lighter color either. If white, I'd go yellow.
It likely doesn't matter much, just thinking of rub marks.
https://www.ritchienavigation.com/
I had one replaced by Ritchie in Pembroke, MA. Give them a call and see if they can repair it or recommend one that will fit in the hole you have. They were responsive when I contacted them in the past.
Looks like a nice job thus far. Sad that these boats are built so sub-standard given the price that is charged. They should take the time and do the transom correctly instead of covering thing up with stainless, plastic and aluminum pieces.
2 batteries with 2 outboards? GW usually has one per engine. There are other items attached, but I've not seen a pure house battery on a GW, maybe on the larger ones?
Id leave it for now. Let it weather in and then try a plastic primer and paint. Primer is INSL_X STIX. Then get some color bars from your paint store, match it up and paint.
Can try GW Cust Service. Wise made the older seats but do not have the patterns anymore. I contacted them 10 years ago and they had a 300 Marlin seat with the SS tube on it. I took it for $150 and it mounted perfectly in my boat. Gave me time to re-do the original and have a spare for swap outs.
I'm not a fan due to the structural integrity concern, but if you do could you make an adapter with smaller dia tubing to put it back in place with a ball lock pin?
Curious, what does a bluetooth receiver cost and why add it to a 20-year-old radio? My factory 2006 GW Kenwood was inside my cabin and when it stopped working I took it apart. What a mess inside from corrosion. the Kenwood is not a marine grade product at all. I went with a new Fusion head...