Learn colour theory with the websites linked on this page.  
Each has apps that will help you learn and create colourful compositions.

The 'Birth of Venus' (right - from the Uffizi Gallery via Google Art Project) was uploaded to KULER, which then created a colour swatch (below).  This was used to create the abstract exercise (below right)  in the Peter Piper Palette Picker on WORQX

Colour was everything for Matisse.  For this project, a colour swatch from his 'The Dessert Harmony in Red' was obtained using KULER. An abstract was created using a type of barcode, and then the colours were applied.  The barcode is a quote from Picasso; it reads 'Every child is an artist'.