Card Labels

It would appear that api endpoint new_card does not permit adding a card level label. Please confirm

It would also appear that put_board_list_card does permit adding a card level label. It says body string as labelIds (plural). Does that mean I can assign more than one label? That is a group of labels that get replaced with the next PUT? If I want to add two labels they are a string with a separator (like a comma) its not clear? How does that work?

Can I assume that the color of the label is fixed? Or that all the labels are the same color?

Are board level labels the same? it looks like I can add many labels to a board one at a time? The color of the label does not seem to be there either ??