They don't lose their stripes as they mature. They'll lose them when they are showing off or feeling good.
If it's dominant in the tank, you'll probably see the stripes missing more often than you would see them present.
If it's not near the top of the pecking order, you'll probably see the stripes often and it'll still color up somewhat.
With regards to the tangerine tigers, I've seen some that I think look great and some that IMO look quite poor. The difference between the two is the barring. I'm not 100% sure what is consider proper vs not proper, but the ones with 'Y' barring strike me as not proper, not to mention they just don't look as good.