thoughts @janfaracik ?

I think there's probably a better fix somewhere, the theme tries to just set colors and doesn't have any other CSS rules (apart from the theme above for codemirror)

I missed that this was in the codemirror theme section - it was just the closest looking bit to css that I understood. Happy to move it elsewhere if needed.
It was hard to test the exact change as chrome developer tools fails to load any of the .scss files, but I arrived at this by editing theme-dark/theme.css which looks to be generated from this?

yes that is the right file.

The right fix is likely in https://github.com/jenkinsci/jenkins

I'm not sure I follow, I think the theme-dark/theme.css file is derived from this file and it doesn't seem to exist in the core. Which makes sense as the core doesn't have any concept of a dark theme?
The core contains _icons.scss which sets the normal colours for the icons, but again has no concept of a dark theme: https://github.com/jenkinsci/jenkins/blob/0f0b023b0f96d795160544d2e56a4add7244c72e/src/main/scss/components/_icons.scss

https://github.com/jenkinsci/jenkins/blob/0f0b023b0f96d795160544d2e56a4add7244c72e/src/main/scss/components/_icons.scss#L74-L77

should probably be changed to be like the unstable one:
https://github.com/jenkinsci/jenkins/blob/0f0b023b0f96d795160544d2e56a4add7244c72e/src/main/scss/components/_icons.scss#L64-L67

So there's a variable for it so we can override the color from black to white without having to change CSS in potentially multiple places

Ah I see now, thanks - I'll look at getting that updated to match