In an earlier blog post, I collected and shared a few online videos of Henri Henche style color studies. Here, Danni Dawson offers a useful demonstration on video of Henche style color study with a slightly different approach. Having studied with Danni, I think her approach is useful because you can easily see the translation of how one might use color study skills in the development of an alla prima portrait.
These studies not only help us learn how to find color and temperature, the experience of transitioning or mixing color right on the canvas creates a sort of "flickering" of colors because they are subtly juxtaposed within the mixing area. Here, little flecks of the "blue" on the shade side of the head probably show through the painting in real life creating a visual vibration (these subtle shifts hardly show up in a video or photos but are beautiful to the naked eye).