Rib and collar are ideally dyed in the same bath, or at least with the same recipe, but the structure, yarn and elastane in the rib make the same shade look slightly different from single jersey. For this reason, for sweatshirts and polo shirts, ask for a lab dip on each structure and approve them together, next to the jersey swatch.
A collar with 3 to 5% elastane absorbs light differently and usually looks darker. It should be ordered from the same dye lot to stay consistent. On dark and pastel colours, the difference is easier to see. At Alteks you can ask for rib in the same colour from the 220-colour card or by lab dip, together with the base fabric.
ribcollarcolour matching
