Apply a primer, if you are using a material other than canvas. Dip a paintbrush in a white or gray primer and paint the shape of a jewel. Allow this paint to dry for about 30 minutes.
Paint a base color using a small paintbrush. This should be a plain but vibrant color such as red, dark blue or forest green.
Apply a second color of paint. The second color should take up the majority of the gem shape, leaving a sliver of the base color. The second color should be two to three shades lighter than the base color. For example, if you painted the gem dark blue, paint the second coat a medium shade of blue.
Paint a third color. This color, four to five shades lighter than the base color, should cover the majority of the second color. Paint over the second color, leaving a sliver of the second color. This sliver should be next to the original sliver.
Apply a fourth color of paint, six to seven shades lighter than the base color. Paint a large sliver along the edge opposite the two existing slivers. Outline this sliver with a fifth coat of paint. This fifth coat of paint should take up about half of the space of the fourth color of paint.