Today, I'd like to show the harmony of colors which are yellow and blue, plus a third color similar to one of them.
Geranium 21cmx30cm (8"x12") - I used yellow, cobalt, and ultramarine in the shadows . Cobalt is a bright pigment and in conjunction with other gives grays but doesn't make it darker.
St. Roch Church in Białystok (21x30) - I did an experiment here. First, with a black watercolor pencil I painted whole picture in a mochromatic way. I didn't draw with it but put it on a piece of paper and using damp brush painted with it as with a regular watercolor. Watercolor pencil after drying does not dissolve as usual watercolor so after it dried I could impose other colors. I painted yellow lights and blue shadows. Green was created by mixing these colors in different proportions, but I added also an olive green. Finally, on the damp paper I darew some black marks with watercolor pencil.
Large Watercolor 33cmx48cm (13"x19") - I used lemon yellow, prussian blue, indigo, and a few orange spots on plants at the window. Watercolor was painted in three layers, each darkening another one in place that seemed to me to be too bright. I used the razor blade and sandpaper to obtain white accents.
The examples above show a rather simple but good color harmony. There are two colors which one is a dominant color, the third nearly one of them (blue plus yellow and orange, yellow and blue plus cobalt, blue, plus yellow and green).
At the end something totally different. Portrait of a girl I recently drew. In addition to the regular drawing with 2B pencil I used graphite powder. In this way, great smooth transition is achieved, the delicate skin and foggy background.