This is a really cool mosaic, and reminds me of a star. The cores of stars are hot, represented by the blue center. As the circle goes out, it gets redder and yellower, which looks like the star getting cooler as you near the outer edge.
This piece of art also looks really calm and serene, with all the perfect circles lined up and perfectly spaced apart. I really love the colors they chose, and the choice to use rectangles to compose the circles.