I have seen Salvation Army church members going to church in white uniforms. Here is a sample image (source).
What is the role of uniforms in the Salvation Army?
Is it compulsory for them to wear uniforms in the church?
This is an old thread but I just found it. As a Salvation Army Soldier who feels called into officership I want to answer this. The SA (Salvation Army) does not do water baptisms, nor do they partake of communion (another story for another time) But we do have the Uniform. The uniform is an outward statement of an inward change much like Baptisms.
As a Soldier of The Salvation Army, I wear my uniform, in the same way others might wear a cross around their neck or something, the uniform identifies the wearer as a soldier of The Salvation Army, but more importantly as a Christian.
This excerpt from the New Zealand. Fiji, Tonga Website answers the questions "Does a soldier have to wear the uniform, and why?"