Got this idea from my shirt... :)
Apply any base coat. I find white as a good base coat.
Like this!! U can be more neat!! :P
LET IT DRY!
Apply your 2nd base of your coloured nail paint.
LET IT DRY AGAIN !
Now outline the dots giving it a haphazard look. Be careful it can also ruin your style.
TA-DA ! :D