Caecilian Question?

First off, pardon me if this is posted in the wrong section, forum, or even website!

I have a question about Rubber Eels (Caecilian Worms/Typhlonectes Natans). I posted this on the general board on FishGeeks.com, but as there is little information on these creatures out there, the moderator suggested I try here. So, here goes:

I have two Rubber Eels (in an aquarium of course). I have had them for about 2-years. When first acquired, they were both black. As time went by, one turned chalky gray while the other remained black. Now recently, the chalky gray one has gotten black spots all over its body as if it is making an attempt to go black again. Is this normal? Does it distinguish sex? Is this a sign of something? I have read that females are larger and tend to be more lumpy, but nothing about color changes?

Appreciate any and all info. Thanks!