S. R. Faruqi:

Apparently there's nothing in this verse, but if we reflect a bit, then several excellences of meaning and structure come to hand. Because of the insha'iyah style, the whole verse has both an interrogative form, and the form of a negative rhetorical question: (1) What is it today, that has caused the rose to take on the color of your mouth, and the tulip to take on the color of your paan? (2) What kind of thing is it, that the rose would be called your colorful mouth, and the tulip would be called mischievous like your paan? (3) What kind of a thing it is, that the rose has adopted a color like that of your mouth, and the tulip has adopted a mischievousness like that of your paan?! That is, this matter is not without fault/vice.

The construction rang-e paa;N too is interesting. Khan-e Arzu has written that when Persian + Arabic, or Persian + Turkish words were conjoined by an izafat, then the breadth of the Persian language has been increased, and is increasing. So by joining Persian, Arabic, or Turkish + Hindi with an izafat, why shouldn't Urdu be augmented? But shame on our 'Ustads', who have virtually closed this off and abandoned it.

Until the time of Nasikh, people wrote rang-e paa;N . See

{1037,5}.

FWP:

SETS == KYA
MOTIFS
NAMES
TERMS

It's intriguing that SRF reads this verse only as one or another kind of a question; on the face of it, it doesn't have that structure. It appears that he's reading an implied kyaa at the beginning of the first line, and then invoking some of the rhetorical possibilities of the 'kya effect'. (Or perhaps there's also an idiomatic usage of kuchh baat hai that automatically registers as a question.) Naturally I defer to his ahl-e zabaa;N judgment in such matters.

But I also like the meditative quality of the literal reading: 'There's something...'-- such that the speaker is ruminating on what exactly it is that causes these (imaginary? real? desirable? inappropriate?) effects. 'There's something there...', 'There's something about it...'-- something in his mind perhaps, or something in the nature of the universe. But in any case it's something elusive, for which the speaker doesn't have the exact words. As usual, it's left to us readers to find them for ourselves.

Here's an example of a similar use of kuchh baat hai ; to me it doesn't feel at all interrogative. From Iqbal's 'Taranah-e Hindi':

kuchh baat hai kih hastii mi;Ttii nahii;N hamaarii
.sadyo;N rahaa hai dushman daur-e zamaa;N hamaaraa

[there's something, such that our [=India's] existence does not get erased
for centuries the cycle of time has remained our enemy]