Acrylics straight from the tube tend to be transparent to some degree, depending on the color saturation of the pigment. But if you want to paint with an opaque palette, you can add white, acrylic’s most opaque pigment. However, it’s good to bear in mind that adding white will distort as well as lighten acrylic colors. To regain the desired hue after mixing a color with white, add other colors in the same family. Alternatively, you can layer a passage with an opaque mixture that’s “off” your intended color, let it dry and then cover it with a transparent glaze of the tube color. When dry, the passage will read as the correct opaque color.