Two Seedlings, different color, Why??

[Cherokee_Motley]

I started both at the same time, but one I transplanted into a 4" cup on March 20th with 50% compost and the other I left in the seedling cup.

I noticed the pure difference in color when I went to transplant the one still in the original container. The one transplanted is light green almost lime in color. While the other is a nice dark green. However, if you notice, the dark green plant is showing a little yellow on a lower leaf.

I have not watered either with liquid fertilizer. What are your thoughts / comments...

Thanks... John