Three things: First, when you change the fluid you're only extracting a bit more than half of the old stuff even if you drop the pan (they hold 8 and change when bone dry). So even though you fed it serviceable fluid instead of junk at 80K, it was still running on about about 45% junk for the last 10K miles. When someone has symptoms at that kind of mileage, I usually recommend doing two quick spill-and-fills in a row to get the junk down to 20~25%. Since you didn't mention any codes or symptoms, simply getting it started on a healthy regimen was what the situation demanded. The new fluid has absolutely enormous film strength, so you can be sure the junk content didn't do it any harm, and like the frog jumping halfway to the door, eventually regular changes will get it so close to clean that the 1mm left between your nose and the door won't matter. Second, all CVT fluids start to brown a bit almost as soon as you put them in. Our '13 Altima has had regular changes at 20~25K forever, and what I drain always looks midway between brown and turquoise. Lastly, a glass isn't really a fair way to evaluate the color. The same compounds in the fluid that lead to the "black gunk" which accumulates in the pan of an unserviced tranny also affect its transparency, so a glass will always make it look far more black and opaque than it really is. The white paper test is a much better indicator, if that has no hint of green or blue then the fluid is in trouble.