Rule: General adjectives precede color and age adjectives.
Examples of errors:
(1) She was wearing a blue long coat.
(2) It was an old big house with a porte-cochère in front of it.
Adjectives of color are one of several types of adjectives whose relative position before a noun can be described in terms of general rules: color adjectives usually follow adjectives indicating age, for example, but precede participles, adjectives of provenance or style, nouns used as adjectives, and adjectives derived from nouns, e.g.:
an old blue coat
a blue riding coat
a blue Chinese coat
a blue fur coat
a blue ceremonial coat
The more loosely defined class of general adjectives (including long), consisting of all those not included in the categories just mentioned, precede both color and age adjectives (cf. (2)):
a beautiful (old) blue coat
When these adjectives occur together, their usual order is as follows: general + age + color + participle + provenance + noun + adjective derived from noun + head noun. For example:
lovely old blue Chinese jade ring
a common old perplexing Chinese city social custom
There are exceptions, of course, e.g.:
On the wall was a perplexing (participle), greenish-blue (color) and obviously ancient (age) carpet