Hey abadtrip, you are VERY correct! The white buckets will let light in, and I can swear by that... This is my first auto grow, but I actually started a different grow about 2 months back. I ended up stopping that grow so I could take those plants out of my tent, so I could get this auto going (better strain choice for my needs). That grow was of 3 different strains in 3 different 5 gallon buckets, and just by sheer dumb luck, all 3 had different light levels.
I had one bucket that I wrapped in foil and then duct tape, so it was completely dark from the bucket (but I forgot about the lid). Then the second one was in a corner of the tent and had regular, silver duct tape wrapped around it (FYI, not good enough to block out light), so 1/2 of it was basically "shaded" in the tent corner... And finally the third bucket was completely white and the light was basically able to flood in from the white bucket sides.
The first bucket had almost no algae...
The second bucket had an algae problem that looked like it was between the first bucket and the third. It was a problem, but it was "save-able".
The third bucket was just "holy $hit" plagued by algae... I actually made another post, asking about my algae problem. I'll try and see if I can figure out how to add a link that will point to that chain... Dunno if I can figure it out when I'm high... Which I currently am! LOL
Anyways, Yes, I have spray painted this bucket. In my other post, I had help from others here. They pointed out my white bucket/light leak issue and told me that spray painting the bucket black, and then white, would block the light and also not attract/retain heat in the water. I have also had to battle heat issues, so the white paint layer was very important. I "highly" recommend this approach for your application! (LMAO I have the giggles right now, and typing "highly" just keeps making me laugh!)