88a62173 ​

input = fill 5v (fill 5h black) |> fold (fold rect) #0
output = [[#1, #2], [#3, #4]]
(OList UList ((VInt, HInt, VInt, HInt), Color), Color, Color, Color, Color)
([{((4v, 4h, 5v, 5h), red), ((1v, 1h, 2v, 2h), red)}, {((5v, 1h, 5v, 2h), red), ((4v, 2h, 5v, 2h), red), ((2v, 4h, 2v, 5h), red), ((1v, 5h, 2v, 5h), red), ((5v, 5h, 5v, 5h), black), ((1v, 1h, 1v, 1h), black)}], red, red, red, black)
([{((5v, 1h, 5v, 2h), blue), ((4v, 1h, 5v, 1h), blue), ((5v, 5h, 5v, 5h), blue), ((2v, 5h, 2v, 5h), blue), ((1v, 5h, 1v, 5h), black), ((1v, 4h, 1v, 4h), blue), ((1v, 1h, 1v, 1h), blue), ((4v, 4h, 4v, 4h), blue), ((2v, 2h, 2v, 2h), blue)}], blue, black, blue, blue)
([{((4v, 4h, 5v, 5h), teal)}, {((4v, 1h, 4v, 2h), teal), ((4v, 1h, 5v, 1h), teal), ((1v, 1h, 1v, 2h), teal), ((1v, 1h, 2v, 1h), teal), ((5v, 5h, 5v, 5h), black), ((1v, 5h, 1v, 5h), teal), ((2v, 4h, 2v, 4h), teal)}], black, teal, teal, black)
([{((4v, 1h, 5v, 2h), grey)}, {((4v, 5h, 5v, 5h), grey), ((4v, 4h, 4v, 5h), grey), ((1v, 2h, 2v, 2h), grey), ((1v, 1h, 1v, 2h), grey), ((5v, 1h, 5v, 1h), black), ((2v, 5h, 2v, 5h), grey), ((1v, 5h, 1v, 5h), black), ((1v, 4h, 1v, 4h), grey)}], ?, ?, ?, ?)