Things You'll Need
Black watercolor pigment
Yellow watercolor pigment
Blue watercolor pigment
Olive green is an elusive color. It's somewhat yellow, somewhat green, and somewhat brownish-gray. It's an essential color in watercolor painting, especially if you're painting realistic things like landscapes. It may be tempting to use a premixed olive green, but you can save money and deepen your understanding of color by mixing your own. Olive green may look difficult to replicate, but you can easily mix it with only three watercolors.
Assemble your materials. It's best to have all your paints in front of you before you start, so the colors won't dry while you're looking for another tube. Get a fresh container of water so the color won't be compromised. Make sure your brush is clean and clear of dried paint that might make the bristles stick together. Touch it to the bottom of the water container to open up the bristles. Find a clear space on your palette, free from runoff from other colors.
Make a puddle of water on your palette. Simply dip your brush in your water container and drip the water onto the palette. How much you use depends on how big of an area you want to cover, and how diluted you want your color to be. Use more water for a lighter hue; less water for a more vibrant color.
Start with yellow. Stroke your brush against the top of your dry pigment until it starts to dissolve, then bring the brush to your puddle of water and mix it in. Repeat this until you have the desired intensity. If you're using tube watercolors, squeeze some into the puddle and stir it up with the brush.
Add blue. Rinse your brush before you dip into the new pigment. This is where you can pick the hue of your olive green – some are bluer, while others are more yellow. Which one you use depends on what you're painting. Try using one-quarter as much blue as yellow. You want a yellow-green and not a true green, because true green will end up forest green rather than olive. You can also mix more blue into the paint later if you want to add darker accents to your painting.
Add black. This is what gives olive green its ambiguous shade. You will want to add far less black than any of the other colors. Rinse your brush and start with just a few drops, then increase until you have the shade you want.
Try using warmer and cooler versions of yellow and blue.
Don't mix too much paint at one time – it will dry up before you can use it all, and you will have to add more water to make it moist again. This can dilute the color.