Ultramarine Blue is in my top 10, probably top 5, favorite watercolor pigments. It's a single pigment color with awesome granulation, and I love to use it with a burnt orange or raw sienna to make interesting neutrals. It's a very "standard" color--it came with all the initial sets of paint I bought when I was starting my watercolor journey in earnest: the Winsor & Newton Cotman palette, the Holbein set, and the Sennelier. I also have it from Daniel Smith and Shinhan.
In my handmade watercolor sketchbook, I have a few pages of paint comparisons since I have duplicates of many colors across brands. (Keep in mind that it's the pigment number that matters, not the "name" the brand has given the paint.) I wanted a quick reference to compare the paints side by side easily, instead of having to dig out my swatch cards.
PB29 is the most consistent color across brands that I've compared thus far. (Please forgive my blooper in the middle there--that's what happens when you don't label paint in your palette and try to rely on your terrible memory.) I used a very high concentration of pigment to water, so you don't really see the granulation here unfortunately.
Some of my swatches show more granulation, but I've been a bit inconsistent with making them so they're not a great comparison either. Each brand has a different way of denoting the lightfastness, and sometimes the "series" (often the price range), of their paint...and I cannot for the life of me remember what any of these stars or letters mean! These do show that PB29 is a fully transparent color, since you can't see any of it over the black permanent marker line at the top.
Ultramarine Blue PB29 is a great all-purpose blue to keep in your palette. These comparisons show us that it can be used nearly interchangeably between brands, so you can pick this color based on price or availability and not notice much difference. The granulation adds tons of interest, and it's a wonderful sky color. And its a single pigment so it will be a clean mixing color for greens and purples. After all, I have 5 different tubes of this pigment and I'm not sad about it at all!
