I could be selfish and take the opportunity to promote my Simple CSS Editor tool, but it would likely be overkill for a single use case like this.... Particularly without testing if it can do what you want.
The quicker solution for you will likely be to look at the Custom CSS section of the Advanced settings in the dashboard. There you can add CSS to locate and tweak the CSS for various tiles on your dashboard.
More importantly.... If you haven't found it already, you may be interested in the Noobs CSS topic....
