In reference to colour or light (rarely, sound): Of fine or delicate quality or nature; soft, subdued; not deep, strong, or glaring.

Pleasing in appearance. Of colour: not strikingly or obtrusively bright; quiet, subdued.

Of colour or light: soft, gentle, or subdued in shade or intensity.

Of colour, light, etc.: mild, soft, gentle, muted. Also, of an object or its appearance: soft in colour or visual texture, esp. as the result of age…

= mellow, adj. (in various senses).

Hence as a poetic epithet of colour: Pure, clear, bright. Also (cf. A. 2b), Quiet, sober.

= ethereal, adj.; spec. (a) heavenly; of or relating to the sky or region beyond the clouds; (b) (of a colour) delicate (rare).

Mature; ripened, softened; made mellow, esp. as the result of age.

Reduced in intensity, strength, or vividness (often applied to colours); toned or damped down. Cf. subdued, adj. 2.

Designating a soft or subdued shade of a colour.

Subdued in colour; consisting of soft colours.

Calm, quiet, composed; cool, sober, collected; undisturbed by passion or excitement. Of inanimate objects: not unduly striking in colour or design…