There is a bug with this theme and the new version of firefox. The bug prevents the profile icon from being displayed, which is shown as white on a white background. Other themes do not have this problem.
Otherwise, this is a really fine looking theme.

Cool

Classy & Sharp contrast

ок

This is still my favorite theme for Firefox. Clean and easy on the eyes.

I used this theme for a few years - it's a great looking and nostalgic theme. However, it's pretty old now (the last release was in 2019), and as a result it doesn't have good compatibility with the new Firefox UI. The "Customise Toolbar" page is broken, displaying invisible white text on a white background. Also, several UI elements are not re-themed, remaining the default light or dark colour.

As much as I like this theme, I've had a better experience with other themes recently, and I think you will too (unless this theme is updated in the future).

Easy on the eyes and a lovely shade of blue. Perfect.

It sure is beautiful... and a mainstay, too!

Четко, контрастно, приятно глазу