i would guess lincoln green and bristol red.. (local plants that were common dye stuff...

a kyrtel is a form of a skirt..

I am guessing...(in parens)

With clothes upon her hed (with clothes upon her head)
That wey a sowe of led, (That were sewn with lead (the metal)
Wrythen in wonder wyse, (?(woven in/worked in)? in Wonder ways)
After Sarasyn gyse, (After the Islamic *guise)
With a whym and a wham, (with a whim and wham)
Knyt with a trym tram (Knit with Trim tram(?))
Upon her brayne pan, (Upon her brown head**)
Lyke an Egyptian. (Like an Egyptian)

or a hat, upon her head, in the islamic style, with metal woven in, to trim it, that she wore on her brown head/hair and looked exotic, like an egyptian!

*guise (like disguise) a word for a style/manner

(**pan or pot or tea kettle is often used as slang term for a head, (as in noggin!)

and yes, a groaning board is like a, um, a "rice table" --the sort of wonderful feast one could order in a dutch/indonasian restaurant years ago!