I believe these are all true. However, it seems that while there are plenty of discussion on how acroporidae can "color up", there is little discussion on color morphing of clams.Just give it plenty of light and make sure you see new shell growth underneath the mantle. Those changes are probably from a different spectrum of light or how the light is hitting the clam. Also, clams have the ability to move or change where the zooxanthellae reside in their mantles. Zooxanthellae aren't the only thing that produces pigment in the mantle.
If we can induce clams to develop higher contrast patterns, or to produce more iridophores, that would really be awesome. (At this stage, I think it's possible)