I'd suggest searching out any Vintage Gliding Club members at your home club (
Vintage Glider Club). The K-6 is still a pretty common type so there's probably plenty iof people who can offer advice. Depending upon which site you fly from you may even find that there's other K-6 owners nearby. Weight, paint type and colour are all considerations (black being good for conscipuity but bad for airframe life!). Don't know if the K-6 is annex 2 or not but that could also affect things too.