the trash bags will give you an idea, but I went ahead and bought some vinyl dye and dyed mine because they are getting replaced anyhow. I hear you on the hot sun, but to me the black buckets have a meaner look to them, they're all drag racing business. I used to like the parchment buckets in pictures until I actually got this car and took a long hard look at them. The parchment is sort of too Park Avenue for my taste.
I think your parchment buckets should look fine with your black door panels on a 69, post a few pictures if you do it.