sonAli is a name from north India and means golden. The root of the word is Sanskrit suvarNa, from su-, a particle meaning good, and varna meaning cover, outward looks, colour, description, letter, note, or quantity, from vR, to cover (cognate with English weir; not to be confused with a completely separate Sanskrit vR cognate with English will which gave rise to words like vara, wish or husband, and varaNa, acceptance). suvarNa had a lot of meanings, including gold, good colour, high caste, wealth, good pronounciation, etc., but the meaning gold or golden hue was very common, and, in that meaning (and a few others), the word contracted to svarNa, which gives sonA in a number of modern languages. sonAli means having the colour of sonA.
suvarNa had been used as a man's name for a very long time in Sanskrit, but the history of the modern name sonAli I cannot say. I have seen it in my childhood, and suspect it is from the eastern part (Bengali), but I am not sure.