I don't really practice any precise "-ism" but if one were to ask me what type of art it is I create, I suppose I would answer with the term "tonal impressionism." I say this because I think that colors have specific moods and qualities and when used together in certain manners, a synergy can be achieved that sets the stage for the subject matter. The subject matter is somewhat secondary to the general overall impression of mood which is achieved via the interplay of carefully selected and limited color palettes.
It is from this standpoint and mode of thought that I conclude that the selection of blue in a painting is perhaps the single most important aspect in the color palette. I am finding that while I may use several yellows and possibly a couple of different reds, one single blue produces the best result for me. Two blues are competitive with one another. The intrinsic mood or soul of the painting is contained in the blue. I do think that sometimes a second blue may be used if in very small quantities for a specific purpose. For instance, I will sometimes find myself needing a touch of cerulean to give a summer sky a bit more power but other than that, the second blue is very very rare.
Some of the characters that I find in blues are:
Cobalt (PB28) - Earthy but bright and warm
Ultramarine (PB29)- Cool and serene
Prussian (PB27)- Unpredictable, wild and moody
Phthalo - I don't have much experience at all with pthalo and it comes in both a red (PB15:1) and a green (PB15:3) shade. But painters I know who use it exclusively tend to have results that are soothing and deep.
Cerulean (PB35)- powerful and transcendent but being opaque and high value out of the tube not a candidate to carry a painting solo. This is the only blue that will augment another well.
There is also the difficult to find Manganese blue that while I've never used I would probably put in a similar category with cerulean. It is relatively opaque and high in value compared to other blues and this makes it difficult to wield in the shadows.
Phthalo is considered to be a Prussian replacement. Due to the unpredictability of the pigment for Prussian blue, it can vary rather wildly in character from batch to batch. Also, it behaves very differently in tints from phthalo which retains it's character more readily while Prussian can have a tendency to get smokey when highly tinted.
I want to caveat the above information: these are my impressions from my experience with mixing and working with color. Even if you have used the same pigments as I have, you may have an entirely different mindset on how you want to accomplish your goals and this may be totally useless to you. But from how I approach and think about color and the goals I want to accomplish, these are my conclusions. I also want to state these characters I perceive are really only useful when you consider how they mix and interact with other pigments and not on their own.