The colored button is the theme selection button. Basically same as Facebook here. It's also now in the message action bar same as emoji, stickers, etc.. selection instead of in the footer.
All buttons have also had their btn-sm classes removed so they're not tiny anymore and are now large enough by default to fit a finger tip in them for mobile accessibility. Below is what this looks like on desktop and mobile currently.
Desktop
Mobile
Note this is not done. Many more design improvements are still coming. Currently my goal is to rewrite all the features utilized by streams first THEN streams themselves will be rewritten and stored in the database instead of dynamically generated on display. Once that's done a big overhaul of a lot of template files will take place to further extract PHP out of them so the templates will primarily be HTML as a template should be.
Next feature to be redone is filters. The new design is already coming along. Below is what it looks like now.
The plan is to support keyword searching, mentions searching, and hashtag searching in it as well.