Hmm, this is not even close to a solution to be honest. The example I’ve shown here is taken from two different instances of Jira. One is default, another one (the white) is customized.
The new cool shiny Jira UI has very limited customization options, and even they are not supported properly. And this makes the products, both Jira and add-ons, looks cheap. Btw, those who make it to the top menu, a typically most used and expensive ones, like Tempo.
Those are just SVG icons. You need to color them in just the way you with other icons in the sidebar with pure CSS. I understand the priority thing, but this is obvious bug in the very foundation of the new UI.
Any chance to have a link for a task to vote?