Dark mode overrides border color in timeline

[migueldeoleiros]

When using light mode the border of timeline items has the same color as the item itself, but dark mode has a rule that overrides the color for all borders, making it look dark gray for all elements.

This is specially annoying when you have a lot of small items since you can't see the color and the whole item becomes dark gray.

Light mode:

Current dark mode:

Intended result (although in this case I disabled all border color changes, ideally the lines in the back would stay with the original dark mode color):

[migueldeoleiros]

The fix should be pretty easy. I don't know much about CSS, so if someone else can work on it I would appreciate it :)
Otherwise I may be able to give it a go