Hi Ronaldus!

Welcome to the amazing world of XOOPS.

(1) GD==is a PHP graphic library; if you use a host, check with them if it is enabled; if you are running your own server, you will need to install it along with PHP
Imagemagick==is a collection of libraries that allows for image manipulation on the fly; again, you will need to check with your host, if it is installed;

(2) This is done in your XOOPS Sys Admin section; go into the piCal admin area -> General Settings, is where you can change the colour settings

Hope you find the info of assistance, and will allow a passion for XOOPS to grow, as most of us have experienced.

Regards

JasonMR