The safest (most upgrade resistant) way of tweaking the appearance of things like this is with a custom tribe-events.css stylesheet – please see our Themer’s Guide for details of setting this up.
With that done, try adding some rules like these – you’ll probably have to do some further adjustment but they should provide you with a starting point.
I’ll go ahead and close this thread – but of course if there is anything else we can help with please do go ahead and create new threads as required 🙂