So I dyed my MTP smock with brown Idye and this is the result. It was pretty hard as the DWR treatment on the outside was impenetrable and the MVP dropliner in the inside also proved difficult to bypass but I managed to pour some dye in via the drip skirt. Not as dark as I wanted an I only used one packet of dye so I'll have a go with a further pack. The Idye poly managed to dye the zip and Velcro a nice brown though and I'm happy with that. I'll post the final article after I've done it over the weekend.