The exercise consisted in using masking fluid to paint the blue backgrounds and save the white for the goldfish:
The masking fluid was painstakingly slow to peel off, left some residue and I ended up scraping paper a bit in places:
I filled the first goldfish with black ink from a Pentel Brushpen (which is awesome for very thin lines as well as large areas) after painting the fins, tail, eyes and mouth in bright orange watercolor:
The second and third goldfish were a mix of bright orange watercolor, black on some fins, eye and mouth, and to cover the masking fluid residue I applied a layer of white watercolor paint:
I framed those and painted the frame bright orange as well before adding a layer of varnish:
