When I pull down the board, I do get a labelNames field, but only one label per color. I have multiple labels sharing a color and I want to list all of them.
There's special call to list all labels defined in specific board by ID, you need to use:
\boards\[boardID]\labels
It'll return json formatted like:
{
"id": "label_id",
"idBoard": "board_id",
"name": "label_name",
"color": "green",
"uses": number_of_cards_that_uses_this_label
}