neutrals and simultaneous contrast

pastel 10x10

If you want to make a high chroma color glow, what do you do? Place it next to a neutralized color, one with low chroma.

This, of course, brings us back to simultaneous contrast.  A color is not defined fully until you place another color next to it. It's all about relationships. For instance, that yellow in the sky didn't vibrate until the grayer/more neutralized violet was placed next to it. If I had place a high chroma rich light violet the relationship would be lost. There would be no yin to face the yang.

A color will appear darker in value on a light ground and lighter on a dark ground, more intense on a more neutral ground and grayer on a very intense ground. Green will look more yellow on a field of blue and more blue on a field of yellow. Size of the color mass also influences the effect of simultaneous contrast. Generally, larger color areas have more influence on smaller color areas.
The gray line going through the two bottom value scales is the same value. Amazing, eh? The lesson for all of us to remember when painting...nothing is in isolation.  Simultaneous contrast is the effect of how color and value are relative.