Very polished, and likely the most on-theme game here.
I really think you need to add a bit more of a puzzle to figuring out the colour codes, at the moment it is just too straightforward. This might also help people remember the codes, which I also had trouble with. Maybe something like short poems or sentences, where you need to infer the colours its talking about. Also, the theme of the riddle could hint at which mausoleum to use the code on, instead of simply telling the player.
An (extremely) simple example:
"Here she lies, wreathed in Poppies, Daffodils and Lavender"
Poppies = red, Daffodils = yellow, Lavender = Purple (or blue)
Tomb: The Lady of the Flowers (or something)
Apart from that, I would suggest reducing the size of the level, there wasn't much point making the player run all over the place.
Apart from that, good job.