Dracula recently posted a link to a list of sandals by hue and the amounts that exist on the shard. Do these amounts grow as more are discovered or looted or are these amounts maxed out? For example if there is only 1 pair of sandals at hue 2120 (made this up, don't focus on it) does that mean there will never be 2 pairs?
For a while sandals could be dyed with the leather dye tub which contained a somewhat limited palette of colors. As of patch 38 sandals can no longer be dyed using a leather dye tub. Patch 38 Dye Tub Changes So unless the sandals spawn on a NPC, are obtained from the bulk order rewards, or are created using a faction tailor (this is a temporary effect) this is it. There is a small chance some additional colors might be released in future events, but nothing is planned yet. UO Renaissance Item Database - Sandals