How do I change the font size and colour of the title of blocks and modules?

The basic lay-out is taken from the installed and used theme CSS. (themes/yourtheme/)
Here you can change/modify the colors, font-size etc. of the blocks, mainmenu..tables etc., etc.
Some of the modules have an extra CSS file (like the newBB, soapbox, wordbook) these can also be changed to the colors, fontsize of your desires.

This Q&A was found on XOOPS Web Application System : https://xoops.org/modules/smartfaq/faq.php?faqid=369