As a rule it should follow that of the walls, a continuous effect of colour with variation of form and surface being a valuable and beautiful thing to secure.

To give the full value of variation--where the walls are plain one should choose a figured stuff for curtains; where the wall is papered, or covered with figures, a plain material should be used.
There is one exception to this rule and this is in the case of walls hung with damask.

Here it is best to use the same material for curtains, as the effect is obtained by the difference between the damask hung in folds, with the design indistinguishable, or stretched flat upon a wall-surface, where it is plainly to be seen and felt.

Even where damask is used upon the walls, if exactly the same shade of colour can be found in satin or velvet, the plain material in drapery will enhance the value of design on the walls.
This choice or selection of colour applies to curtains and portieres as simple adjuncts of furnishing, and not to such pieces of drapery as are in themselves works of art.

When a textile becomes a work of art it is in a measure a law unto itself, and has as much right to select its own colour as if it were a picture instead of a portiere, in fact if it is sufficiently important, the room must follow instead of leading.