You'll need some pain black or navy canvas shoes, I got mine from topshop in the sale for only £10.
Take the laces out and tape round the soles of the shoes to keep them clean.
Start dabbing blue paint all over the shoe with a sponge.
Gradually add the purple and pink paint in various places. Mix white paint in with some of the colours to give a more dimensional look to the background. Try to alternate where you put the different colours so each shoe doesn't look too similar.
This step is optional but I dabbed little bits of white paint around the shoe to create the effect of clouds.
With a really thin brush dab small dots of white paint randomly around the shoe, if you do this in a pattern it will not look as realistic. You can also flick paint over the shoe to create varied stars. Add a couple of bigger stars by crossing two lines over each other. Then paint around the lace holes white to make it look more polished then remove the tape and put your laces in and you're finished!