I have had SW paint mixed at 50% so I don't see why it wouldn't work for BM paints.

Ask the person who mixes it how light it would look, they can give you an idea so that you might want to go deeper with it, you don't want it so light that it's just a really pale pastel or maybe you do.

I don't want pastel, but also don't want to do laundry in a cave either. I am so torn, cause I know in my mind one of these is what I am looking for just not so intense.

You can create your own custom color.

Ask the BM salesperson what is the "base color" for Affinity (or Atmospheric or whatever color you like). The base color is the light-colored paint they start with when they add pigment to create Affinity.

Then buy a quart of Affinity and a quart of the base color.

Take them home and play around with them. Mix up small batches and try them out on your wall. Paint at least a foot square. Look at the colors in all kinds of light... day, night, etc. Keep your mixtures in little tupperware containers. Don't mix too much at once!

When you get the color you want, paint a square of cardboard (about 6" square) that color. Take it into BM. They will put it under their color reader and mix you up a gallon (or however much you want) of your own custom color.

I've done this lots of times. It's fun.

oooh fabulous idea mclarke! I am new to paint, I spent sooo many years in Army housing and white walls in every one of em leaves my head spinning at all these choices!
Thanks a bundle!

Is there a reason you feel it would be cave like. Do you have any natural light in LR.
I have BM Mount saint anne in a basement windowless washroom and it it is not dark at all, and I think it resembles your two affinity colors. So maybe one of your colors would be fine as is.