That's normal, all boas have some degree of iridescence. BRB's just have the most by far 
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Thanks,
Dave "Rainbows-R-Us"
0.1 Wife (WC)
0.2 kids (CBB)
2.7 Brazilian Rainbow Boa (adult breeders)
2.5 Brazilian Rainbow Boa (sub-adult from 2004)
4.8 Brazilian Rainbow Boa (sub-adult from 2005)
2.1 Hypomelanistic BRB
0.1 Het for Hypomelanistic BRB
0.1 BCI "Elvira" normal from 1989
1.0 BCI Albino / het-anery
0.1 BCI Hypo / het-albino
0.1 BCI Anery / het-albino
0.1 BCI Salmon (possible super)
1.0 BCI Albino het stripe
1.0 BCI Salmon
0.1 BCI Ghost
0.1 BCI Super salmon, possible jungle
1.0 BCI Salmon, possible jungle
lots.lots.lots feeder mice and rats 