In the following posts, I will briefly cover color transparency,local color, and color pigment differences.
Color Transparency and Opacity
Transparency of a color (how much you can see the paint color under it through it) and opacity affect the way you use the color. If you misuse a transparent color, trying to make it opaque, you will be very frustrated with the results. Watercolors are usually transparent. (Some have particles that make them a bit opaque, and addition of white to water colors makes them opaque. In fact, “gouache” (goo-AHSH) is the name for opaque watercolors.) Most acrylics are semi-transparent (except for white). Many oils are transparent. Paints that are not very transparent can be made more transparent by mixing them with a “medium” and thus making them more transparent.
Examples: Alizarin crimson, ultramarine blue, lemon yellow, cobalt blue, burnt sienna, and viridian are highly transparent. Cadmium yellow is semi-transparent but doesn’t work well as a transparent color. Cadmium red, Cerulean blue, and light red are opaque. Flake white is more transparent than titanium white.
Gamblin Paint Supply discusses different transparent and opaque palettes on this website, http://www.gamblincolors.com/oil.painting.techniques/palettes.html
You can test the transparency of the colors on your palette by drawing a dark or black line with a permanent ink on your drawing surface, then laying each color over the line. Some will cover it. Some will not. Also mix the colors to see what shades the various combinations make.