There are three different pairs of Aliens in the slime eggs, you can identify which pair you're going to get by the serial number embossed on the bottom of the egg. I know the one ending in 77 is the Green/Glow in the Dark pair; the other two pairs are Orange/Grey (76), and Greenish-Grey/Red (78).
I ended up merging all three slime pools into one big mega-pool, I'm planning to use it to slime up some of the Lanard stuff I got, and use it in the old Kenner Queen hive Playset.