When I first started painting my “Moods of the Minch” seascapes (the stretch of sea between the Isle of Skye and the Outer Hebrides is called the Minch) I used Prussian Blue, Burnt Umber, and Titanium White as the main colours. At times, the only colours.

Adding a cadmium yellow gives grassy shore greens, lichen on shore rocks yellows, and sunset colours. Adding magenta gives the pinks of the seathrift and purples of sunsets. Removing red from my palette as using it was how I kept ending up in murky mixes, and using magenta wherever I would have used red instead. Add lemon yellow which is a lighter, transparent, bluer (cooler) yellow, perfect for daffodils. Plus a black (PBk31) for sheep, one that when mixed with white leans into green, and mixed with yellow produces beautiful landscape greens.
For me Prussian Blue gives a sense of the cold Atlantic Ocean and dark showery weather, with a tremendous range from deep dark to very pale. It’s one of those “a little goes a long way” colours, and the way to control it when colour mixing is to add a touch of it into another colour rather than adding into a pile of the Prussian. It remains my favourite blue, and ultramarine remains my least.
When I started exploring using coloured grounds rather than working on the white of the canvas, and after a life painting workshop with Alan McGowan where I came away with the mantra “build a bridge between the orange and the blue”, I really got into blue plus orange mixing. A single-pigment orange mixed with a blue, plus white, is now a fundamental part of my palette. It gives a wide range of brown and grey, and because every mix is derived from the same two colours they all harmonise. (It needs to be a single-pigment orange because one that’s a mixture of red plus yellow goes into greens when you add blue, not useful for painting a seascape.)

I expanded the cadmium orange plus blue possibilities by using different blues, and worked with this for some time. Then I bought every single-pigment orange I could find to see how different oranges would work. Of these, Transluscent or Transparent Orange PO71 was the one I enjoyed the most, and this is now a standard on my palette too. It’s a transparent pigment, so mixes differently to Cadmium Orange, which is an opaque pigment.
The next colour I added was Dioxazine Purple, to explore purple plus yellow colour mixing and using purples in shadows. Made hideous murky messes with yellow, but discovered that mixing it with orange did beautiful things.

Moving to northeastern Aberdeenshire, I found I myself on seashores with red sandstone, a colour that wasn’t mixable with a palette that didn’t include red. So that’s been added this year though I haven’t got a favourite yet.

There’s one other colour that I use as an ink, but not as a tube colour, and that’s Payne’s Grey. I enjoy it for continuous line drawing. It’s softer than black, having blue in the mix. Mostly I’m using it as a strong dark, not as a mixing colour.
Thank you. That was helpful.