A very intense deep blue that was discovered by accident in 1935. It has all the good points of Prussian Blue but not its problems so quickly replaced the older color for most uses. Unlike Prussian Blue it comes in several shades from cyan to deep greenish to quite reddish deep blues. It is permanent in all mediums. It is very transparent and so powerful that manufacturers need to use extenders in the making of the paint otherwise it would be too difficult to use.
Chemists soon discovered that preparing Pthalocyanine with Bromine produced a beautiful deep transparent green. Pthalo Green has largely replaced Viridian as the artists main dark green color.