Between manual gathering and Crush specialists, keeping Red Paint stocked isn't hard. The Crush route is less effort once you've assigned the right Pokemon to the job.

Colors items red

Raw Material
Leppa BerryCrushCrushRed Paint
ShopSmearguru / Palette Town Shop
Bleak Beach (Smearguru hut), Palette Town (Level 5)
PawmoCrushGeodudeCrushGolemCrushAurorusCrushConkeldurrCrushElectivireCrushLarvitarCrushShieldonCrush

You can craft Paint Balloon Brown, Paint Balloon Orange and 3 more using Red Paint. These 5 recipes are mostly Other items that help fill out your island.

5 recipes
Paint Balloon BrownOther
Red Paintx1Green Paintx1›
Paint Balloon OrangeOther
Red Paintx1Yellow Paintx1›
Paint Balloon PlumOther
Red Paintx1Blue Paintx1›
Paint Balloon RedOther
Red Paintx2
Paint Balloon RoseOther
Red Paintx1Pink Paintx1›