Ultramarine Blue vs. Phthalo Blue (Thalo Blue)


Matt Smith started a discussion with his students on which blue is warmer, Ultramarine Blue or Thalo Blue. To start, they are both blue and blue is the only primary color that is by nature cool, so they are cool (the other two primaries are warm). From that point on, it’s a matter of degree and perception. Any comparison from there is based on any color or set of colors that are next to it and an artist’s personal sensitivity to color (those variables are vast but close). Some suggest not to assign warm or cool to a color until you lay a second color down, but the hard truth is, blue is a cool color, and yellow and red are warm. Now, we have warm and cool blues, reds, and yellows, but those differences can be subtle and are reinforced once a second color is laid down. Once a second color is laid down, we can compare. When we compare, those subtleties kick in and things get tricky. For instance, how can a warm color like red be cool? It doesn’t have to be cool, just cooler than the initial red, or compared to that second color. Add yellow or red to blue and it’ll warm up. It can still be blue, as in the case with the initial question here, but it’s starting to warm.

Some artists would say yellow is warmer than red or vice versa. But, for many, it’s a matter of personal color perception. To Matt, a mixture of the two (orange) is the warmest warm, talking from a visual standpoint. Deciding which of those two colors is warmer is a matter of your personal reaction to color. So, make these calls by comparing back to the three primaries. Does it lean more to red, yellow, or blue? And which of the warms do YOU find to be warmer? Make those decisions, and you have the answer. Everything else is a discussion or argument over opinion.


“Think clearly folks. Don’t look for formulaic answers here. Understand warm and cool in its simplest form (red, yellow, and blue) and judge from there.” - Matt Smith


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