What’s the plural for a group of Richard III’s?

"Coal-black is better than another hue, in that it scorns to bear another hue; for all the water in the ocean can never turn the swan's black legs to white, although she lave them hourly in the flood."

—Titus Andronicus, William Shakespeare

#ShakespeareSunday

I charge and command that, of the city’s cost, the pissing-conduit run nothing but claret wine this first year of our reign.