Acrylic on Stretched Canvas
22 x 28 in/56 x 71 cm
I bought a tube of Pthalo. I have used Pthalo and what's also known as Primary or Brilliant blue (by some manufacturers). I knew they were the same by comparing their pigment colors, which are listed on the tube (except for the cheapest paints). Pthalo is PB15, that is, Pigment Blue15. Brilliant blue is also PB15, so they the same color. If you don't know what I'm talking about, learn more about pigment numbers and the color index--it will help you in building your own personal color palette.
Modern Prussian blue is actually a hue, which I'm sure you know means that it is a mixture of several pigments. Golden Artist Colors acrylic Prussian BlueHue is PB15 (or Pthalo), PV23 (Violet 23), and PBk9 (Black 9). The development of Prussian blue has an interesting history--here's a link to read more.
Anyway, I know both of these blues will need to be used with caution, at least until I (or you) get used to them. That's because Pthalo is a very strong, in-your-face, bright blue that leans to the green side. It's really good for some types of water scenes and also for adding--just a touch, however--to ultramarine blue skies.
And Prussian blue, well, let's just say it has a dark personality and leave it at that.