Blue Ironclad beetles color.

[Two Crows]

One of my blue ironclad beetles is much darker than the others. What could be the reason for that?

 

[Goliathus]

One of my blue ironclad beetles is much darker than the others. What could be the reason for that?...

Moisture absorption.  See coloration section of the following page - 

https://www.aquarimax.com/how-to-keep-blue-death-feigning-beetles-asbolus-verrucosus/

 

[Two Crows]

Thanks! Very good info.