I don’t do many pics of Ferris and wanted something to provide kind of a reference
Ferris’ “blood” is highly mutagenic and allows him to shift his form, however when he does shape-shift he is still blue and orange as he is when a bat because it takes a lot more to out of him to change colour.
Because of this, he will use darkness to disguise himself stalk prey. That said, even when in darkness, you can tell it’s Ferris as his eyes will always glow.