Not exactly a WordPress plugin or learning but a really useful tool when working with websites or doing any type of design work and changing colours is ColorSchemer ColorPix. It is a tool that allows you to grab the pixel colour under your mouse and gives you the Pixel Size, RGB, HEX, HSB and CMYK codes. I used it extensively when changing the colour scheme of a WordPress template by checking the HEX colour then searching for that code in the style sheet.
It’s a handy tool and most importantly it’s a free download!
