Purple was for centuries the most expensive colour a workshop could buy. The original dye came from sea snails in quantities that made it worth more than gold by weight, which is why it ended up reserved for rulers by law in several places. The rules are long gone; the association stuck, and purple still reads as ceremonial in a way no other colour quite manages.
Velvet suits it better than any flat weave, because the pile holds the colour at two depths at once - dark where it lies flat, bright where the light catches the tips - so a purple velvet panel is never the single heavy block that purple paint would be.
The judgement our master Indian artisans make here is about restraint at the other end of the bed. With a headboard this saturated, a footboard carved as densely would leave the eye nowhere to rest, so the footboard is given a single book-matched panel and the carving is kept to its crest and base. The bed has one voice and one echo, not two arguments.