Universal Colors

Universal Colors are those colors that tend to be flattering to most people.

Maybe it would be correct to say colors that will most likely not be unflattering.

They may or not be one of your Power Colors, but they usually won't be one of your worst, either, especially when paired with the rest of your seasonal palette colors.

Universal colors are not overly bright or dark and not too warm or cool. This is why you might find a lot of uniforms in many of these colors.
Below are colors that have been traditionally considered universal. Different people differ about specific colors, but these are the colors I've found most often cited.

The Turtleneck Test - determing if a color truly flattering

However, I am becoming more stringent with my views of what is considered truly universal.

I devised my own 'turtleneck test' to see if a color is genuinely universal. This test filters out many of them. Some of the colors may indeed be flattering on some people. My definition of universal, however, means it should be genuinely flattering on everyone (maybe not a power color, but definitely deserving to be in one's official palette).

Stone, a medium-to-light grey, is often listed as a universal color.

I did, indeed, included it in all of my previous swatch versions. But I had to accept that shade does nothing for me nor any truly warm seasons. I took it out. Now I either include a warm grey or putty color in those muted warm seasons that flow into a cool season, a muted cool season that flows into a warm season, or I skip it entirely. 

As you can see in the photo above, the cooler stone color is not dreadful. It's better than, say, a cobalt blue or similar color on this person.
But warming up the grey is better.

However, choosing from their best neutrals, in this case, a warm sand, is best for this Autumn woman.

Last word about universal colors: they are good choices when you can't wear one of your best colors.