Lighter colours generally help a room feel more open because they reflect natural light more effectively.
Soft neutrals such as white, cream, light grey and pale beige often create a brighter visual impression and help smaller rooms feel less enclosed.
Blinds that closely match wall colours also tend to make the window area feel less visually dominant, which can create a more spacious effect.
Where a room receives limited daylight, lighter fabrics often help maximise brightness throughout the day.
That said, colour should still work with the wider room design rather than following one rule. Seeing fabric samples in the actual room often makes colour decisions much easier, which is why we bring samples during our free consultation service.