Is it permissible to answer questions regarding the beauty of a prospective fiancée (such as the color or nature of her hair) for someone who intends to propose to her or for a colleague of his, and is it permissible for the suitor to see a picture of her before she adopted the hijab?

The ideal way for a man who wishes to propose to a woman is for him to look at her himself. There is no objection to delegating another woman to look at her, based on the hadith (definition) of Umm Sulaym: "Smell her front teeth and look at her Achilles tendon." As for delegating a non-mahram (definition) man to look at the prospective fiancée, scholars have differed on this, between permissibility when there is no fear of fitna (temptation/strife) and prohibition. It is not permissible for a sister to describe a woman's hair to her male colleague who is not an agent of the suitor, based on the Prophet's (PBUH) saying: "A woman should not touch another woman and then describe her to her husband as if he is looking at her." It should be noted that there is a danger in mixing with ajnabi (non-mahram) men if it leads to khalwa (definition) (private seclusion), tabarruj (display of adornment), or khudu' bil-qawl (softening of speech).