Because angels’ clothes correspond to their intelligence they also correspond to what is true, since all intelligence comes from divine truth. So it amounts to the same thing whether you say that angels are dressed according to their intelligence or according to divine truth. The reason the garments of some angels gleam as though aflame, while the garments of others shine as though alight, is that flame corresponds to what is good, and light to what is true because of that good. The reason some garments are pure white and soft white and do not shine, while others are of various colors, is that divine good and truth are less dazzling and are also differently accepted among less intelligent people. Pure white and soft white correspond to what is true, and colors correspond to different shadings of truth. The reason angels in the inmost heaven are naked is that they are in innocence, and innocence corresponds to nudity.
from Heaven and Hell, Section 179
Secrets of Heaven 