Excursion into Green

I did some oil paint mixing charts this morning to learn about the greens. In the upper chart all colors have the same value and fading towards gray in each column. The yellow on the upper left is a mix of cadmium yellow medium and burnt umber, the blue on the left is coelin blue tinted with white and the greens in between were mixed from these two. The decrease of saturation downwards was obtained by adding a neutral gray.
What surprised me was the left column, which appears fairly green, not brownish. It doesn't come out quite as clear in this photo than in the original chart. So at lower saturations my color judgement "that's green" stretches much further towards the warm colors than I thought.

Even the indian yellow in the left column still appears slightly greenish, although I used a warmer gray to decrease saturation compared to the first color chart. 
To find a color observed in a landscape it is usually not necessary to know which exact mix of paints is used. In fact, most of the observed colors, especially the grays, can be mixed from a large number of  tube paint combinations. Matching a color is much of a try and error game using the paints one has on the palette... Lighter or darker, more saturated or less, warmer or colder. 
However, this game can go wrong when some of the observed colors are not within the mixable range of the paints on the palette. And I think this is exactly what happened to me in some of my paintings with fairly light greens. I often did not have a warm yellow on my palette and I tried to mix those warm greens from cad red and cad yellow, which did not give suffiently high saturation and looks chalky in relation to other colors matched more accurately. 
> So is all you are trying to say that one needs a warm yellow on the palette?
Yes :-)