I have a cube that switches between black and white, but only if the room is lit with a white color will it be white. How can I make the cube white regardless of the lighting?
You tie the texture to the “Emissive” slot instead of the “color” slot.
Note that a full-bright cube won’t look cube-like, because it will have no side shading at all, making it look like an ill-defined blob. Instead, you will likely want to split the color half-way into base color and half-way into emissive. (Multiply the texture by 0.5 and then send it each way.)