Did you try thermofilm? It is made for fabrics that don't like water. I could imagine, that the color change with watersolvings is caused by residuants of stabilizer, that cover the filaments of the yarn. You could try the thermofilm, where you iron away the stabilizer. It is supposed to be very gentle after removing, too - so perfekt for your silk embroidery, maybe. Good luck!

I have heard of it but not used it. Thank you for the recommendation. I am always keen to try new products.