The official scheme for the tidewall is a fairly cream white and tan, personally I recommend a purer white.
Tau buildings are traditionally colored a pure white in artwork anyways, and it's already a color in your scheme (and a rarer one by the looks of it, so it won't be overdone). I know I plan on making mine pure white for similar reasons. One, it's the inverse of my urban scheme which primaries black armor with some white. Two, like the way it stands out on the board; it symbolizes the sterile purity of the greater good and imposes itself on the battlefield.
But tan is good too for camo and practical reasons