A reader can only recall so much. Best practice then is to keep character appearance descriptions concise, using concrete nouns to describe details that are memorable and distinct from other characters.
He was bald as a stone and he had no trace of beard and he had no brows to his eyes nor lashes to them. He was close on to seven feet in height and he stood smoking a cigar even in this nomadic house of God and he seemed to have removed his hat only to chase the rain from it for now he put it on again. (Blood Meridian, Cormac McCarthy)
Be careful of details that are too trivial to define a character. Generic eye colour is not defining. If a character has no inherently striking details, such as the purple tail of some fantasy character, then choose details one might use to point out the character in a crowd. ‘Her, over there, with the red hair’, rather than, ‘Her, over there, with the brown eyes.’ With highly significant details, such as a character having a peg leg, it is useful to write these as line endings, which have a greater propensity to linger in the reader’s mind.
So powerfully did the whole grim aspect of Ahab affect me, and the livid brand which streaked it, that for the first few moments I hardly noted that not a little of this overbearing grimness was owing to the barbaric white leg upon which he partly stood. (Moby Dick, Herman Melville)
In long-form stories, such as a novella or novel, it is also important to re-mention the character’s appearance from time to time, though not as a full description like when the character was first introduced. Instead, integrate one of their features into some description. Exploiting the environment is a means to achieving this, ‘a sudden gust tousled her red hair’; a character action, ‘she wiped a tear off her freckled cheek’; the current lighting, ‘moonlight silvered her gapped-tooth smile’; and so on.