The blue - green deep rich color of spirulina is caused by the presence of a specific pigment called phycocyanin. (well-beingsecrets.com)
Broil until everything is nicely charred, about 10 minutes (you want lots of deep rich color so don't be afraid if some of the edges get pretty black). (cookingchanneltv.com)
Solid colors: deep rich color without shading. (snowyswan.com)