If you have ever painted a room in your home or your home's exterior, you more than likely have a little paint left over. You should keep that paint in case you need to touch up paint an area in the future. If you have paint in a color that you no longer have in your house (or on the outside of your house), there are several ways to get rid of the leftover paint.
If you have a quart or more of paint left, consider donating it to a charity, school, theater, or a paint contractor. As long as it is not dried out, paint is valuable (even in crazy colors).
If you have several cans of latex paint that you are not using, consider mixing them all together to get a custom color. This color can have additional pigments added to it to make a color you desire or can be used as is for a base coat on your next painting project.
Did you know that there are paint recycling centers? Search online for paint recycling centers in your area. Each center will have its own rules for dropping off paint to be recycled, so check with them before showing up with your leftover paint.
Don't forget to recycle the cans your paint came in. Check with your local recycling center for their rules regarding recycling paint cans. Often paint recycling centers will also take the paint cans.
Don't Just Trash It
If you throw leftover paint straight in the trash or pour it down the drain (especially if you have a septic system), you risk creating an environmental hazard. Here is the proper way to dispose of your extra paint.
If you have latex paint leftover, you can dry the paint out then throw it in the trash. If you have 1/2" or less of paint left in the can (or other vessel if you recycled the can), simply open the can and let it dry out for a day before throwing it in the trash with the lid still off. If you have more than 1/2" of paint left, you can add kitty litter, sawdust, shredded newspaper, or special paint hardeners found at home improvement stores to your latex paint to hardened it before throwing it in the trash. Make sure it is completely hardened before throwing it away.
Oil Based Paint
Oil based paint is more hazardous than latex paint. It should never be put in the trash. Contact your local recycling center or garbage disposal company for where to dispose of oil based paint properly.
If you have old cans of spray paint that need to be disposed of, simply spray out all of the old paint onto an item that can be thrown in the trash. Dispose of the painted item but save the paint can for recycling. Keep in mind that the paint cap is usually made of a different material than the paint can so they should be separated prior to recycling. Never puncture a spray paint can.
Only Buy What You Need
If you have a lot of extra paint left over from a project, try to only buy the amount of paint that you need next time. You can use a paint calculator to make sure you get the correct amount of paint.