You need to use one of the conditional tenses (or moods) here.
If the boy is holding a paintbrush, ready to splatter his brother (i.e. there's a real possibility that he'll do it) use the first conditional: If I spatter the paint on my little brother and get him covered in red, blue, and yellow, willyou still love me ?
That is not what I meant. You could say "I just spattered paint on my little brother; do you still love me?" However, if you have not actually painted him yet, it is a conditional situation (If I did...) and you use would instead of do.