Cissnei wears the Turks' standard uniform consisting of a black suit, white shirt, black tie and black loafers (or black boots and other footwear in some cases) with a pair of black fingerless gloves while on duty. When Final Fantasy VII first came out without its prequels and sequels, the Turks were seen wearing navy blue suits as opposed to black suits both in-game and in the concept arts. As Final Fantasy VII evolves into a compilation, Turks members are seen wearing black suit in both prequels and sequels to the original game. Although the Turks have not made an appearance in the Final Fantasy VII: Remake trailers as of the time this is written, in my opinion, it is quite possible that their suits will be adjusted to black to match the rest of the compilation.
At some point in the game, when Zack speaks with the two 2nd class and 3rd class SOLIDERs in the corridor of the SOLIDER floor, they will ask for his opinions on who he thinks is the hottest girl in Midgar. Zack is then given the choice between Aerith, Cissnei and himself. If Zack chooses Cissnei, the 2nd class SOLIDER will comment that he thinks Cisseni looks hot in her black suit.
It is interesting to note that Cissnei is one of the rare Turks membmer that does not wear her uniform all the time. At the very least, when she goes on "vacation", she wears the proper attire (a sporty swimsuit). In one of Zack's DMW (Digital Mind Wave) sequences with Cissnei, when Zack and her followed Tseng off the beach to their mission, Zack asked Cissnei if Tseng wears his suit everywhere he goes and Cissnei teasingly asked Zack if he was hoping to see Tseng in swimming trunks, hinting that there is a high probability that Tseng does wear his black suit everywhere he goes.
In Final Fantasy VII, when the Turks (Reno, Rude and Elena) went on vacation in Wutai, they were spotted wearing their suits as well (albeit they were just drinking at the bar and not vacationing on the beach).