Inspired from nature.
the triangle shape is inspired from an icicle, and the colour selection is from feeling or atmosphere in winter time.
the air of winter time is chilly outside(=gray) but warm inside(=yellow), and also feeling melancholy(=purple).
"cocoons of silkworms"
white silkworms would make beautiful strings and be coloured sometimes.
"a change of leaves"
Leaves turn their colour green, yellow and brown. This colour combination seems like progress of live and death.