I like the idea of the tree waving (as it does, more than the ones around it) so why not waving goodbye? Perhaps 'make a mosaic'; apart from the alliteration, make sounds less formal. Should yellow red and brown be moved up a line?
the aspen waves goodbye
to multi-coloured leaves
which form a mosaic on the ground
between lawn and compost bins
yellow red and brown
/ and a single robin enquires what I’m doing there / if I can’t turn over earth, just go away!