This time I was successful
I realised that I am in fact using the wrong side of the fabric (and will continue to do so) and the right side is actually grey with black herringbone and a bright blue pinstripe. The wrong side is black herringbone, with less of the grey, and the blue stripe being less obvious.
(A few times recently I have chosen to use the wrong side of the fabric deliberately, and I will continue to be fearless in this, if the effect is more what I want).
I'll be careful when assembling to make sure I have all the black sides out.
The fabric is a mystery remnant from the stash and I can't recall where I bought it, and have no idea of the fabric content. Its not 100% poly as it presses quite nicely. From the slight damp animal small when pressing it wet I am guessing it has some wool content, though it doesn't have any itchy feel to it. (So myabe its viscose/rayon then and its a damp vegetation smell not a damp animal smell.....)
Good progress made on the trousers today. They now only need inner leg seams, waist facing and hems, I gave the outer leg seams a good press and left them on the ironing board to cool and dry.
I decided that tonight was not the night to burn the midnight oil and try to finish the trousers off.
I think I'll have a nicer finish if I take a little time tomorrow and finish them nicely.
The only thing I've done differently on this pair is to add 4 belt loops and a slightly deeper shaped waistband, otherwise they are the same as the previous pairs made from this pattern.
Hopefully as a pair of black trousers, but with the slight interest from the textured fabric they will be useful in the wardrobe.
No pictures as half sewn up trousers are not very inspiring IMHO.
But I will post a hanger shot once they are done.