Instructions
Log in to your "Neopets" account.
Make sure your Starter Paintbrush is in Your Items. If it isn't, check your Safety Deposit Box and move it over to Your Items with your mouse.
Click the "Shops" button on the menu and select "Rainbow Pool" ̵2; the blue dot with the rainbow on it.
Select the Starter Paintbrush from the bottom of the screen, and then click on the pet you wish to paint. The selected pet will change color.