Yepper. I did.
I wasted hundreds of dollars buying yellow strain after yellow strain only to have them almost all die off on me. Too sensitive. Heck they would go belly up if I looked at them funny. I think out of hundreds bought I had something like 5 or less left. In desperation I decided to try to make my own hardy strain of yellows, so I crossed them with reds.
The result was yellow off spring and red offspring. After several more generations I was able to have a pure yellow strain that was pretty hardy. This is where my Sunshines came from. Not too long ago (yr? 2 yrs?), I bought another strain of yellows for another tank for a good price. These were the type that hardly had any yellow. I mixed some sunshine culls with them from my astax project, and the resulting offspring generations later have been bright and beautiful and much more hardy.
My point is, it is possible to mix yellows and red, and then breed them out again. It does indeed make a much hardier strain. Problem is other people who have tried it have wound up with wilds. I think the color genes are in different places, and you kind of luck out as to what strain you get when buying from someone. The only way you know is by gambling and trying. Working with shrimp colors can be very frustrating.