Shields changes its color when takes damage due to DV. Also they are damaged when crafted depending of the color.

When shields take damage, their color change.
Seems that the problem is the color is defined by Data Value (damage).

Something similar happens when crafting shields: black shields has no damage, and white shields has 165 points of durability.

I have also found that, for example, when trying to apply a banner model to a yellow shield (DV 11), it gives a black shield. But, if it is damaged and the data value is 91, the banner cannot be applied.