Now, the grays will be different, of course, because the colors are not the same. You'll get different results. If you want a warm gray then combine red and green. Orange and blue will make a cooler gray-which is great for the shadows in the snow.
Let's try something fun. I can't tell you why this works but it DOES and every time, at least, for me. If you take a pure color, like red, and stare at only that, close up, for about 30 seconds-then quickly look at white you will see the complimentary color! It's a great exercise for children. They love it but adults get a kick out of it, also. Ever noticed when you are gazing on a shadow that is kind of colored-like one off a blind-when you look away you won't see that shadow color anymore? I bet you saw the complimentary color and didn't even realize it! Try it.
Art History Moment - The reason why Leonardo Da Vinci's fresco's, such as "The Last Supper" are in such disrepair is that Leonardo did not take the right time with his frescoes. To rush the process he painted in tempura on a dry wall. This is not actually a true fresco-there can be no corrections as the painting moves forward this way. Because of this short cut method much of his work was already in disrepair by the 16th century. If he had used the true fresco method of painting into the wet plaster it would be in a lot better shape today-for us to enjoy! Luckily we have clever art restorers that have painstakingly tried to recreate Da Vinci's original intent. Thank goodness for the modern science (and I say "science" because it is) of restoration. These guys really do make miracles happen.