Handprint site says about this:
PB 74 Winsor & Newton cobalt blue deep is the most saturated of the paints listed here; it keeps its deep warm hue even when applied full strength; it also has a lovely gentle flocculation that appears in all mixed greens, blues and violets made with it. I sometimes prefer PB73/74 to ultramarine: it is just as lightfast but is less transparent, shows very little color shift as it dries, and creates a wonderful downy granulation in mixtures. It mixes perfectly with other cobalt pigments, providing a complete range of blue and green shades with the same textural and handling attributes. The only drawback: like ultramarine, cobalt blue deep will fade if exposed to mild acids (fresh lemon juice or vinegar may be strong enough).
I have successfully weaned myself off my addiction to W&N Burnt Sienna. I have found a number of more saturated paints in Daniel Smith (some too strong!) and am currently enjoying MaimeriBlu’s Transparent Mars Brown (PR101 – the same pigment as W&N. Most other ‘burnt siennas’ are PBr7 are more opaque)
I also perhaps should try MMB Transparent Mars Red (also PR101) as well. Don’t worry I plan to do a page of my Burnt Sienna explorations soon as I am not sure which paint i am going to take with me on my trip