Find a section
Right at the start, you need to find yourself one section in the picture. One section means, that an abstract picture usually has a lot of sections inside it. There are boxes, or even different areas that you consider are not part of the other. Therefore, take things slow, and start painting the border of one section. This will help you understand which colour you want to give to one particular section.
Find different sections
Once you are done with finding the first section, now is your time to find other sections inside the picture. You have to draw a border line with different colours on different sections of the picture. This will help you as you will be able to differentiate between different sections which you want to colour separately. Try to be specific when you are trying to colour areas with a different colour and try not to overlap the same colour over and over again and it will not look nice.
Fill the sections
Once you are done with the borders and you are done with selecting different colours for different sections, it is now time for you to start colouring. If you have used red colour on the borders of one section, now take the red colour and start colouring inside the borderline. You have to complete each and every edge inside that section with the colour red so that one of your sections is complete. When you are done with one section, do the same with other sections of other colours. Since you have made a borderline of different colours on different sections, fill the inner section with the same colour.
Once you are done with colouring all the sections, it is now time to make the whole thing presentable. Get the picture framed so that you can present it in front of others.