Correction:
"All years of the Prius had oil usage problems."
It's the nature of the beast. When you start/stop an an engine 20-50 times a drive vs. once, things get wonky.
My solution to the oil color issue was to not change it for 40,000 miles. I added about 20 qts of oil as needed. Actually, color had nothing to do with it. Working two jobs and not caring enough about my salvage title '08. 195K miles, and the **** thing won't die.
While many obsess about keeping the oil at the top mark, the conventional wisdom is that the oil level doesn't matter in the Prius as long as it's between the two marks, and that's about 1.6qts difference. If you can visually confirm your level is between the marks, you're good to go.