Here is a Rembrandt showing great handling of warm shadow colors.
Here are some of my favorite mixtures for use in shadows. Your monitor will be different than mine, but I think you will get the idea. perhaps you could make these notes quickly on your palette in order to really see them for yourself. You long time painters out there are probably rolling your eyes as this is pretty basic, but I am trying to cover the entire subject of landscape painting and there are many painters who are not deeply experienced who may need this information. I will try to throw some grad level information in soon.
Above is ultramarine and burnt sienna. Where the two are intermingled is the created shadow color. I have lightened them with a little light below. This is a great workhorse mixture. I often lay pictures in with this one. They are near compliments and give a note than can be varied from warm to cool and still remain full of life and glow.
This is ultramarine (I threw a little white in there so it wouldn't appear black on the monitor. Making this mixture the white is probably unnecessary) and quinacridone red. You might have alizirin instead of quinacridone. If you have the permanent alizirin or permanent rose, you are using quinacridone already. This gives a nice purple that goes well into shadows on a sunny day in an impressionist painting. In the lower note I have pushed yellow ocher into it, to "step" on it so it will be grayer. Yellow being the compliment of violet that takes it towards gray. I use this a lot also.
This is cobalt violet (my favorite color) and yellow ocher, the two colors mix in the middle to make a glowing shadow note that is on the warm side.
Here is viridian mixed with quinacridone (or alizirin) to make a particularly dark note. If you don't carry a black, you can make squids ink with this mixture. Below is the note with some white in it.
I want to caution you that these are "stems" for creating shadows. You should still observe the actual shadow and choose among these and doctor them up to fit your situation. There are no recipes that are universal, so these are only starting points.