2 different recipes. Brands sell different pigment mixtures under this name, so they won't all look or mix alike. Compare the pigments below; the most common is PB29 Ultramarine Blue.
Who makes it
PB29 Ultramarine Blue2
- Old Holland Classic Oil Colours No. A244PB29LF ISeries A18 ml tube* · 40 ml tube · 60 ml tube* · 125 ml tube · 225 ml tube · 475 ml tin* · 1000 ml tin*About Old Holland
- Schmincke Mussini Resin-Oil No. 10492
PB29 Ultramarine Blue + PR259 Ultramarine Pink + PV19 Quinacridone Violet / Rose / Red1
- Grumbacher Pre-Tested Artists' Oil No. P307
Sizes are the ones each line is sold in; marks a size only some colors come in. Check the store for a particular color.