Blloc mentioned that the decision to retain the colour of profile pictures is to make it easier for you to find the people you want to talk to - I presume this is more because a profile picture (and subsequently the colours in them) can play a helpful role in finding a Conversation faster. If you’d like request, the wishlist or Ratio4 thread is always there for your feedback!
There’s are some unofficial threads about customising Samsung phones (example here and here); if it’s of interest to you, do check it out! It’s very unlikely that Blloc will come up with a theme for a specific device, considering that it’s not inclusive of the Ratio experience. In my opinion, these community themes look great either way!
I hope this helps!