Opal Paint in its day was one, if not the first, 24bit painting program for Amigas. It was very good for professional work. Then new Amigas, and better options appeared, but for a couple of months the Opalvision+OpalPaint were the best combo you could find at an affordable price.
OpalPaint+Opalvision could happily work in both NTSC and PAL formats while the Toaster was only NTSC in its entire Amiga life. Furthermore, the Toaster was more expensive.
Thanks to the hard work and tenacity of Toni Wilen you can emulate an Opalvision and actually use OpalPaint with WinUAE.