Are you using any type of adapters on the HDMI port? Also those screens are during POST, does the problem exist once you are into the operating system? I am not sure this forum post may help but you can have a look.

HDMI signal is digital, not analogue (like Composite / RGB) therefore color loss is very unlikely to be introduced via loose connection (although sometimes bad electric contact may play as filter for some frequencies).
The problem is either on the end generating this digital signal (MB defect or CPU {e.g. Intel HD Graphics 630} if it's onboard, or GPU if it's add-on card, sometimes insufficient PSU can introduce these glitches, sometimes extra color profile/drivers configuration but very unlikely for boot step) or receiving end - monitor/display (but you're saying this problem exists with even if display is changed, likelihood of multiple displays having same defect is quite slim, same applies to PCs - likelihood of multiple PCs having exactly same defect is relatively low), there's some chance of electronic interference might cause this issue (strong EM field in operating environment).