Very bright colors, little to no orange wash on the sides, and a fair amount of blushing are what I look for.

The orange wash tends to turn brown as they age so you want to avoid that in a baby, the brighter colors as a baby, the better it will look as an adult since they tend to darken, nice blushing on the sides and back will compliment how it looks as an adult.

No matter what some people may claim, I beleive that if you want to breed pastels (or cross them into other morphs), you want the best one you can find. Don't settle for an ugly, dull one. A few people will tell you it doesn't matter what the pastel looks like as long as it's a pastel. Well, that's why there are so many garbage pastels out in the market. People went for quantity instead of quality. Some pastels for sale don't even look like a pastel should.

The one in my avatar had no orange on the sides as a baby. At 500 grams it still has bright yellow coloring. Trust me. Stay away from the ones with all the orange on them. There are a few on KS right now that have a TON of orange on them and they are priced dirt cheap. When they age, you understand why they were so cheap.