I also chose to install the UBBT77 styles and I then got problems identifying the new vs old.
The last update date should display a newer date for the new styles. Additionally, if you hover over the preview link, the newest styles will have the largest id number.
Oh I see the report flag and it melts in, I'm thinking can one make it red like the little "NEW" icon so it stands out more?
You can customise your forum by editing the post_gallery.tpl, post_side.tpl, and post_top.tpl template files and inserting a custom styling entry on the Fontawesome flag icon such as:
<i class="fas fa-flag titlebar-item" aria-hidden="true"></i>
<i class="fas fa-flag titlebar-item" aria-hidden="true" style="color:#d30303;"></i>
But this would be a discussion for UBBDev as modification support is not provided at UBBCentral.