Fluorescent ball pythons...I kid you not.

[asplundii]

Would it even work with ball pythons? The rat's hair doesn't glow, would scales? I don't know that much about the genetic make up of scales so I have no idea.

This is why I said you need the genome sequence to first before you take the next step. In these specific mice the hair does not glow but there are GFP animals that have glowing hair. ANDi the monkey is an example. IIRC the rabbits have glowing hair too... If the GFP tag is specifically inserted in a chosen location one could get them to glow, even in a patter specific manner. If you just do a pell mell GFP insertion then who knows what will and will not glow...