Hello Clair.
Three weeks is virtually no time at all. In the early stages the mucus might be any number of colours. I suspect that the brown will probably be old blood from the stitching and the healing process. My mucus was never white or clear until a year or two out from surgery. Indeed, it was often hard like pooh, smelt terrible, and would get stuck in the anus just like its predecessors. However, with patience and sometimes a little help from anal irrigation, it gradually cleared in colour, improved in texture, and was much easier to manage.
I'm sure you will get there eventually but, in the meantime, I'll leave you with a rhyme, written to ease my frustration at the time.
Best wishes
Bill
RECTAL STUMP MUCUS.
If there’s one thing’ gives me the hump
it’s mucus from my rectal stump.
They did not tell me this would be
a side–effect of ostomy.
With no faeces coming through
no way did I expect this goo.
It is so inconvenient
that I am still incontinent.
I thought that this would be all cured
once my ostomy matured.
However, it’s not gone away
and I fear it’s here to stay.
Sometimes brown and sometime white
but mixed with blood is never right.
Then there’s yellow and there’s cream
which will flood out like a stream.
Sometimes it’s soft and sometimes hard
sometimes it’s slippery just like lard.
Occasionally I’ll get a chunk
but mostly it will look like gunk.
The mucus used to irritate
and refused to irrigate.
That method didn’t work so well
although it minimised smell.
When I reflect, I must admit
sometimes I get fed up with it.
For I was not expecting this
every time I have a piss.
With both a plug and inco’ pad
you’d think it would not feel so bad.
But I still moan, and I will grump
about the mucus from my stump.
B. Withers 2012
(In: My Ostomy World Trilogy 2014)