Improve jump to unread button

[ajbura]

Description

Fixes #213

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings

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[N-R-K]

Hi, don't think this is important enough to warrant opening an issue, so just leaving it in here:

The current color on the unread bar doesn't fit well with the rest of the color theme, at least on the butter theme. It's too bright compared to everything else around it.

I would suggest using something lighter, maybe something like #4f6662 would be more fitting.