Palazzo pants are usually worn in warm weather, and chiffon is practically synonymous with summer. So if you combine them, you have the ideal summer-wear. Of course, white or beige are more summery colors than black, since they tend to keep you cooler by reflecting sunlight. But the advantage of black is that it goes with anything and tends to be more formal. Whatever color you choose, you are sure to look great in flowing wide legged pants.
Three examples that I like:
Black chiffon palazzo pants pictured:
Left: Somo Lite Women’s Fold-over Flare Wide Leg Slinky Boho Palazzo Pants
Middle: DAYISS 3 Colors Womens Chiffon High Waisted Long Pants Palazzo Slacks Split Leg Skirt (Black)
Right: SUNNYCI Womens Elegant Loose chiffon wide leg Pants Trousers Skirt
Palazzo pants, no matter what the color or fabric, can often give the impression of a long skirt.