Retail hardware stores offer many types of tints and pigments, typically in the paint department. Check the labels to determine their suitability for use with joint compound. In a pinch, you can mix semi-gloss paint with joint compound, but the safest approach is to use tints specifically designed for coloring joint compound.
After you add the tint according to the manufacturer’s directions, apply the joint compound as you normally would. Before you start your project, test your tinted compound on a scrap piece of drywall. Try different color intensities and note any color changes that occur after drying. Your final results might vary widely among different tint manufacturers so test various types if you’re after a specific effect. Seal the joint compound with a clear interior primer to make the new surface water-resistant without hiding the tint.
Experiment to create interesting color patterns. For a splotchy effect, mix the tint and joint compound just enough for a streak of tint to run through the compound. Layering different colors is also an option. For example, add sky-blue tint to some compound, apply it and let it dry. Then add a pale yellow tint to a new batch of compound and apply that over the dried blue compound. Finally, use a wet rag to wash away the dried layer of yellow compound, revealing the blue underneath.
Tinted joint compound also works well for texture applications. For example, instead of sanding joint compound smooth after it dries, some drywall professionals leave distinctive trowel marks to create a rough texture. The tiny nicks and blemishes mimic the appearance of plaster walls. Adding a brown or yellow tint to the joint compound, before applying it, can enhance the effect, resulting in an aged but elegant texture.