The passing room faces north and never takes direct sun. That is not thrift, it is so the light holds steady — and even so, the same bolt does not read the same at nine in the morning as it does at four in the afternoon.
North sky light drops from something over 7000K to nearer 5000K across a day. Satin throws that light back off large unbroken floats and more or less straight into your eye, so when the source cools the face cools with it. A matt plain weave scatters instead, and barely shifts — which is why this is only ever a problem with the satins.
Colour is passed between half past nine and eleven, all year. Outside that window it goes into the light box under D65 or it does not get passed.
Sample cards carry the same note. A customer once compared a card under warm gallery lighting and told us the colour was wrong; they took it to a window and it was right. That was our fault for not saying so, and it has been printed on the back of every card since.
Bring a swatch, a drawing, or just a sentence — "it should drape without going soft" is enough to start. We work backwards from yarn count. Minimum run 30 metres.