It's a huge painting, nearly four meters wide and two-and-a-half-meters tall (12' 9 1/2" x 8' 6 1/2"), and is painted with a palette limited to three colors: red, green, and blue. I think it's a painting that shows why Matisse has such a reputation as a colorist, particularly when you compare the study to the final painting with its glowing figures.
In her biography of Matisse (on page 30), Hilary Spurling says: "Those who saw the first version of Dance described it as pale, delicate, even dreamlike, painted in colours that were heightened... in the second version into a fierce, flat frieze of vermilion figures vibrating against bands of bright green and sky. Contemporaries saw the painting as pagan and Dionysian."
Note the flattened perspective, how the figures are the same size rather than the ones further away being smaller as would occur in perspective or foreshortening for a representational painting. How the line between the blue and green behind the figures is curved, echoing the circle of figures.
"The surface was coloured to saturation, to the point where blue, the idea of absolute blue, was conclusively present. A bright green for the earth and a vibrant vermilion for the bodies. With these three colours I had my harmony of light and also purity of tone." -- Matisse
Quoted in "Introduction to the From Russian exhibition for teachers and students" by Greg Harris, Royal Academy of Arts, London, 2008.