As much as I hate self-criticism. You’re coffin is milestones ahead my poor quality coffins :’(
As for the colures try brown and then a darker brown of the same colure to replace the “horrible” pink and light red lines. You might want to try very dark drown instead of black and add some flaws like some branch marks. Other then that I think the colours agree with one another and some gold never misses.
There is just one thing if I may don’t you think the coffin is a tad big?