With paint suppliers promising to match the colour of any plush pillow or team jersey you bring in, tinting paint on your own without the benefit of a paint shaker is no longer a necessity. In fact, some paint shop chains offer iPhone apps that let you take a picture of the colour you want and the application will do the work of picking their matching shade. Once you get your paint home, however, it might look different in your lighting than it did in the store, so you may want to adjust the colour on your own.
Add a few drops of colour from your tinting tubes to your base colour. To determine which colour tint to add to your base paint, refer to your colour wheel. The three primary colours are red, blue and yellow. Yellow + Red = Orange; Yellow + Blue = Green; Red + Blue = Purple. Adding a little black tint to a base paint will mute the colour to a dusty shade.
Stir the tint into the base paint using the paint stick, making sure to blend well. Remember that tint will separate from the paint so mix well to prevent streaking.
Paint a test patch of your newly tinted colour on the surface you intend to paint using your paintbrush. Colours change as they dry, so make sure your sample patch is completely dry before determining if you've achieved the desired tint. Also make sure you're painting your sample patch on the surface you intend to paint rather than on a test board or cardboard for a true sample of the final colour. The tint of your paint will reflect the colour around and beneath it.
Repeat steps 1 to 3 until the desired tint is achieved. Once your sample patch is a match for your desired colour, give it several more thorough stirs or take it down to your local hardware shop and ask them to mix it in their paint shaker.
Remember, there is no tint that can lighten your paint colour; it can only deepen and darken it. So add your tints in stages to deepen and darken to the desired shade. You can always add more tint, but you cannot remove it. The only way to lighten paint colour if you've added too much tint is to add more base colour, which will result in wasted paint. While it is possible to tint paint using pots of other paint colours rather than tubes of tint, you will also be adding bulk to your paint supply. For example, if you want to turn a gallon of white paint light blue, you might use half a tube of blue tint. But if you use blue paint instead, you'd need almost an additional 2.25 litres (1/2 gallon) of paint to achieve the same colour.
The tints in the tubes are not paint; they are simply pure colour, meaning they have no binding agent. If you attempt to apply tint directly to your surface, it will not stick.