The speaker watches colors move and describes them almost like a performance. Reds and oranges swirl together in a dance, rich and deep. Then a pale blue arrives, soft and cool, like a winter sky, and streaks across the red. The title, "Colors of the Trees' Song," suggests the speaker is picturing autumn foliage as music, with each color playing its own part.
The mood starts out calm and admiring, then grows more intense. The reds "pulse" like a heartbeat, which makes the scene feel alive rather than still. The speaker seems fully absorbed, noticing small changes in color and feeling them almost physically. The ending is sudden: the colors burst in an "explosion," then fall to the ground like leaves. That last comparison is quietly clever, since the colors have been leaves all along. It leaves a mix of excitement and gentle sadness, as the peak of the display gives way to its end.