Mixing all three traditional primary colors creates a muddy brown, as expected, but why do we get mud when mixing other colors? It's due to the undertone often called color bias.
Sometimes referred to as 'mud,' it happens when you mix paints to the point where no original color, hue family, or new color is evident.
Usually, when we mix paint, we want vibrant secondary or tertiary colors. However, nothing undermines color harmony more than clashing undertones.
Tone
Each tone has a unique combination of hue (color family), value (light or dark), intensity (brightness or dullness), and temperature (cool or warm).
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Paint colors are at their most vigorous intensity when they are straight out of the tube. Colors may vary from manufacturer to manufacturer, depending on the manufacturing process (i.e., different ratios of additives, mediums, or pigment impurities).
TONE is a single or isolated color swatch with a unique combination of color characteristics. Note that tone may also be defined as any color mixed with gray.
TINT is any tone mixed with white (in drawing, it would be the lighter marks or the paper's white).
SHADE is created from the addition of black or dark (in a drawing, it would be a darker mark or darker pencil).
Masstone
Painters may refer to masstone as 'body color,' 'top tone,' or 'mass color.' Masstone is the actual color of the paint we see straight from the tube, applied thickly enough to completely cover the surface.
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It appears when the paint is undiluted, highly concentrated, or applied in a generous thickness, so that light cannot reach the substrate below to reflect off it. Note that if the color is too dark, you may have to add a slight touch of white to determine the masstone.
Masstones within the same paint color family may vary slightly from one paint manufacturer to another, depending on the manufacturer's process or amount of pigment concentration.
Undertone
The undertone may be seen when a paint color is spread thinly over a white surface and may often be concealed when a color is viewed in isolation.
The undertone becomes apparent when the color is compared to another color swatch or hue within the same color family.
Masstone vs. Undertone
The masstone is what you identify first; it's the color family or hue. The closer the undertone is to the masstone, the truer or more vibrant the color appears.
In some colors, the masstone and undertone are very similar; in others, the undertone is quite different from the masstone. For example, some reds lean more toward yellow and orange on the color wheel, while others lean more toward violet or blue.
Finding the Undertone
Skilled painters use their experience to take the guesswork out of this process. However, for those just learning, brushing paint swatches thinly onto a white ground, with one next to another, is the simplest way to find the undertone.
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| Red Oil Paints Manufactured by Holbein |
Warm undertones have more yellow. Cool undertones have more blue. The red oil paint tones may look similar at first glance, but when compared, you can see subtle warm or cool undertones.
Understanding how to select the correct colors, or when mixing, is essential, but choosing the accurate color with the right undertone is even more critical for mixing vibrant colors. The mass tone and undertone should work together to create a harmonious color scheme or lean toward the color you are mixing. If you are interested in learning more, check out color bias.
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Updated January 1, 2026.
