My legs are getting tired much sooner when going down the same blue trails when it has got more than 6 inches of fresh powder and I am scared of going on black runs(I am scared of fall in the powder). I also find myself constantly trying to slow down which wore my legs up quickly.
Keep in mind that the trail ratings are relative. A blue is easier than a black . . . for a given mountain AND snow conditions. I ski blacks and even a few double-blacks confidently in powder out west but mostly skied blue terrain the few years I had another reason to be in the northeast during ski season. Blacks with icy northeast "snow" are not for me.
When you are learning to deal with powder, stick with the blues and don't feel bad about the idea. Note that a green with 6 inches of fresh snow is unlikely to exist and might not be a good idea because there isn't enough pitch to keep moving.
At Alta there are only green, blue, and black trail ratings. However an ungroomed black with two feet of fresh snow obviously is very different than the same terrain when it hasn't snow for a week. Neighboring Snowbird has black, double-black, and triple-black terrain. Even so, a steep black groomer at Snowbird requires different technique than a black tree run or black in an open bowl after a snowstorm.
A story from Alta a dozen years ago when I was an adventurous intermediate:
I was with schoolmates who were advanced/expert skiers during an Alta Lodge alumni gathering in April. Had missed the intermediate group because I was taking my tween daughter over to ski school. My schoolmates said they would do a warm up run on a groomer with me. But when we got to the top of the Collins lift, they realized the Ballroom rope drop had just happened. That meant fresh tracks. I knew just enough to be willing to head out the traverse since I was with them and had rented somewhat wider skis that day. But when I was about to drop in where the terrain is "blue" my classmate shouted that I had to keep going farther out. The pitch in the blue terrain wasn't steep enough for how deep the snow was that day. Of course, she was right. After I managed to get down with a couple of stops but no falls I went off to ski groomers. Or at least fresh powder on top of a groomed surface only a few inches below.
To start getting a sense of how different 4-6 inches of ungroomed snow feels, look for places that you can just go straight for a bit and then plan on making one good turn that gets you pointed back uphill to slow down and come to a stop. Then repeat. If there is powder on the side of a groomer, that can be a place to start.
