Attaching Colors to Trailer

Does anyone know if there is any particular way that the colors attach to the vision target? If not, easy enough to attach them via screws, or the always-useful duct-tape, or, most likely, velcro. The plans on the FIRST website give detailed instructions on how to construct the vision target itself (TE-09010) but nothing mentions how the colors attach to that.

Also, when constructing our vision target, we reused a previous year’s bot’s polycarbonite. The plans emphasize leaving the plain white plastic covering on. Due to the fact that we had already used this polycarbonite, we did not have this covering. Is there a particular reason they requested this, and if so, will any white covering do? The only reason I can think they would need the white covering would be in order to prevent the hue of the colors from being changed by the polycarbonite, but for that, any white material would work…anyone know? Thanks in advance.