My family and friends primarily use Messenger, and we like the chat themes and custom like buttons and gifs and nicknames and other silly features. People are allowed to like different things.
Even though I have the exact version mentioned in this post, I have been unable to find any flags in the debug menu that will enable the ability to change colors in a chat conversation. For some reason neither the post or the telegram channel it links to, do not mention which flags to enable. I've seen it mention on other platforms that "bugle.enable_custom_themes" is the specific flag, however that does not exist on the current beta version as far as I can tell. The version I have and the one mentioned in the post is messages.android_20240125_01_RCO0.phone.openbeta_dynamic.