East-facing rooms get bright, cool-toned direct light in the morning and flatter light for the rest of the day; west-facing rooms get the opposite pattern, with warm, golden direct light in the late afternoon and evening.
Versatile mid-toned neutrals tend to cope well with the daily swing in an east- or west-facing room, since they don't rely on one specific light quality to look right.
A colour chosen only by how it looks at one time of day may look quite different a few hours later in these rooms specifically.
Testing advice
View a sample at both morning and evening before deciding, since these rooms change more across the day than north- or south-facing rooms.
Lighting simulations and descriptions here are approximations, not exact physical predictions — see methodology.