With the "Earth Palette" I can use a mixture of Ivory Black and Titanium White to make what appears to be the color blue.
When using an earth palette, this mixture does NOT make gray, really!
All of the so-called “blue” in my paintings are made from this and you can see it in the examples below.
In fact the blue from an Ivory Black and White mixture is so "electric" I often need to tone it down by adding some reds and/or yellows.
If I wish to deepen and enrich an area of this mixture of "blue," I could glaze a little French Ultramarine or Prussian Blue over it....but rarely, if ever, need to do this.
None of the examples below have any glazed colors to make the blues look bluer - they are all a black/white mixture - and most have yellow or red added to calm it down.
The drapery behind the figure is purely black + white. The black/white mixture in the sky is cut with raw umber and raw sienna.
I added a little red into these black and white mixtures to get a blue that is a bit on the purple side.
The sky is basically black and white with some reds added for warmth near the horizon line. I darkened and slightly neutralized the blue at the top of the canvas so as not to draw the eye upwards.
Again, the black/white mixture needed to be cut with raw sienna because it was much too bright for a background.
I began the blue checkered tablecloth by mixing a thin glaze of French Ultramarine + Ivory Black to sketch in a pattern of checks over a plain white painted cloth underneath.
When it was dry, I matched the paint value with the black/white mixture and covered it up in order to create the ilusion of a blue checkered tablecloth.
Of course, the shadow areas were a darker black/white mixture with raw sienna added for warmth (shadows are supposed to be warm).
Take a peek at my black & white sky at:
With this particular earth palette, I cannot paint a landscape and make a sky look "natural" if I use any blue paint on my canvas.
When I was learning to paint, I copied the Old Masters - I especially learned most of what I know from Vermeer. I quickly learned that I was unable to duplicate the colors unless I eliminated the blues.