Wow, thanks for the long entertaining threads. I too hope you get the pictures re-uploaded soon.
A chimera is an organism with 2 sets of genetic information, usually resulting from a two eggs, as oceanblue explained in the original thread.
Because of this, it's features are the result of two sets of genes expressing themselves. A chimera (Pirate) that produces eggs or sperm, creates them using only one set of genes(the one that developed the sex organ). Thus this coloring cannot be passed genetically.
Interestingly a mutation allowing for increased chances of chimera can be passed. It would have to be selected for by looking for eggs with 2 embryos in them rather then the strange coloring.
I think in general this is likely to reduce the life span of the Axolotl produced, but I have no evidence of that.