Mashup to change the properties of a css class

Hi,
We use TP to present results of our sprint.
Now we are pushing the time boards, but we have a problem: when we project it (with a projector) the contrast of the "tau-cell-planner i-role-cell-planner" is not enough.
So I would like to change it to a color easier to see...

I think this could be done with a mashup that changes the background color property.
Could you provide some hint to do so?

Thanks