S. R. Faruqi:

For ṣubḥ shiguftah gul huʾe tum there are two meanings: (1) you've become the flower that has bloomed at dawn ( ṣubḥ shiguftah = having bloomed at dawn); (2) at dawn, you bloomed like a flower.

In the first meaning there's more freshness and dramaticness. As long as the beloved was juvenile, she hadn't seen the ways and styles of the world/age; she had no idea how attractive and compelling her beauty could be. At that time she was hidden in the garment-hem of one lover alone, the way a bud is hidden in leaves.

But when the beloved attained the state of youthfulness-- that is, she became the flower that has bloomed at dawn-- then the way many people look at flowers that have bloomed at dawn, she too became the object of the attention of thousands of desirers. Now, the poor initial lover no longer has any special status.

If it's taken in the second sense, then the point emerges that until yesterday you were a newly-sprung bud; at dawn today when your youthfulness burst out, then thousands of viewers emerged to see you. In this meaning the beauty of the scene is greater. Because it's often been seen that girls very quickly cross the threshhold from childhood to youth. That girl who yesterday seemed to be a child, suddenly becomes flirtatious.

To use kalī ke rang to mean 'like a bud' is also fine, because rang is a word that has a zila with kalī .

FWP:

SETS
MOTIFS == VEIL
NAMES
TERMS == DRAMATICNESS; ZILA

This ghazal is the first of a set of two about which SRF makes special claims for an over-all 'musical' effect; see {1589,1} for his discussion.

It's a pity that 'ogle' is now pretty well archaic, because it's just the right word. 'To stare in an impertinent, flirtatious, or amorous manner' is just what suits the sense that naz̤z̤ārah here seems to have. (Its spelling has of course been altered to suit the demands of the rhyme.)