Unless they are color coded, you just have to take potluck with a mix. Atleast you know you have two different kinds. There are quite a few round cultivars in various shades of green and a few yellows. Are they hybrids or open pollinated, The hybrids can be narrowed down a little bit.

Thank you for responding. The seed pack does not say if they are hybrids. The mix is called "Billiards Mix" and contains "Eight Ball"(dark green), "One Ball"(yellow), and "Cue Ball"(light green).
After studying the seeds a bit longer, I could tell that the larger seeds had differences...one large and flat, one rounder and plump. I put two of each type of seed in 8oz cups to start. We'll see how it goes. Thanks again. I'll post later in the season with the results.

I did some additional searching and found that they are hybrids:

Here is a link that might be useful: summer squash info

Yep those are the Hollar sisters. Cue Ball, the light green one is the best performer for me. One Ball is pretty and yields well at times but is more tempermental. Tends to turn dark green at high temps, but you should not have that problem. Eight Ball is the older sister and a solid performer, though not up to Cue Ball.