31aa019c ​

input = fill 10v (fill 10h black) |> fold (fold rect) #0
output = fill 10v (fill 10h black) |> rect (#1, red) |> rect #2
(OList UList ((VInt, HInt, VInt, HInt), Color), (VInt, HInt, VInt, HInt), ((VInt, HInt, VInt, HInt), Color))
([{((10v, 8h, 10v, 8h), green), ((4v, 10h, 4v, 10h), grey), ((3v, 10h, 3v, 10h), blue), ((3v, 1h, 3v, 1h), red), ((1v, 8h, 1v, 8h), grey), ((1v, 4h, 1v, 4h), blue), ((9v, 9h, 9v, 9h), green), ((9v, 7h, 9v, 7h), blue), ((9v, 2h, 9v, 2h), teal), ((8v, 5h, 8v, 5h), blue), ((8v, 3h, 9v, 3h), blue), ((8v, 2h, 8v, 2h), grey), ((7v, 2h, 7v, 2h), yellow), ((5v, 3h, 5v, 3h), teal), ((4v, 3h, 4v, 3h), blue), ((3v, 6h, 3v, 6h), red)}], (6v, 1h, 8v, 3h), ((7v, 2h, 7v, 2h), yellow))
([{((1v, 4h, 3v, 4h), blue)}, {((10v, 6h, 10v, 6h), grey), ((10v, 5h, 10v, 5h), yellow), ((8v, 10h, 8v, 10h), grey), ((8v, 1h, 8v, 2h), yellow), ((5v, 1h, 5v, 1h), brown), ((3v, 10h, 3v, 10h), brown), ((2v, 10h, 2v, 10h), orange), ((1v, 10h, 1v, 10h), green), ((1v, 6h, 1v, 6h), green), ((1v, 2h, 1v, 3h), orange), ((1v, 1h, 1v, 1h), red), ((9v, 9h, 9v, 9h), green), ((9v, 8h, 9v, 8h), grey), ((8v, 6h, 8v, 6h), blue), ((7v, 9h, 7v, 9h), blue), ((7v, 5h, 7v, 5h), green), ((7v, 4h, 7v, 4h), orange), ((7v, 2h, 7v, 2h), grey), ((6v, 9h, 6v, 9h), green), ((6v, 5h, 6v, 5h), red), ((4v, 8h, 4v, 8h), blue), ((3v, 8h, 3v, 8h), fuschia), ((2v, 9h, 2v, 9h), green), ((2v, 4h, 2v, 4h), brown)}], (2v, 7h, 4v, 9h), ((3v, 8h, 3v, 8h), fuschia))
([{((10v, 3h, 10v, 3h), grey), ((5v, 10h, 5v, 10h), blue), ((2v, 10h, 2v, 10h), teal), ((1v, 5h, 1v, 5h), teal), ((1v, 1h, 1v, 1h), fuschia), ((9v, 7h, 9v, 7h), green), ((7v, 4h, 7v, 4h), orange), ((7v, 2h, 7v, 2h), blue), ((6v, 6h, 6v, 6h), fuschia), ((4v, 4h, 4v, 4h), blue), ((4v, 2h, 5v, 2h), brown), ((3v, 7h, 3v, 7h), grey), ((3v, 5h, 3v, 5h), red), ((3v, 2h, 3v, 2h), orange), ((2v, 9h, 3v, 9h), red)}], (8v, 6h, 10v, 8h), ((9v, 7h, 9v, 7h), green))
([{((8v, 10h, 10v, 10h), orange), ((9v, 1h, 10v, 2h), black), ((5v, 1h, 5v, 4h), orange)}, {((10v, 9h, 10v, 9h), fuschia), ((10v, 3h, 10v, 3h), blue), ((10v, 1h, 10v, 1h), blue), ((9v, 10h, 9v, 10h), red), ((8v, 1h, 8v, 2h), grey), ((5v, 10h, 5v, 10h), yellow), ((4v, 10h, 4v, 10h), teal), ((1v, 7h, 1v, 7h), orange), ((1v, 6h, 1v, 6h), grey), ((1v, 5h, 1v, 5h), red), ((9v, 3h, 9v, 3h), green), ((8v, 8h, 8v, 8h), orange), ((8v, 7h, 8v, 7h), fuschia), ((8v, 4h, 8v, 4h), green), ((7v, 8h, 7v, 8h), yellow), ((7v, 6h, 7v, 6h), brown), ((6v, 7h, 6v, 7h), orange), ((6v, 4h, 6v, 4h), teal), ((5v, 5h, 5v, 5h), yellow), ((5v, 2h, 5v, 2h), yellow), ((4v, 5h, 4v, 5h), green), ((4v, 3h, 4v, 3h), teal), ((3v, 7h, 3v, 7h), green), ((2v, 7h, 2v, 7h), red), ((2v, 5h, 2v, 5h), fuschia), ((2v, 4h, 2v, 4h), grey), ((7v, 7h, 7v, 7h), black)}], (?, ?, ?, ?), ((?, ?, ?, ?), ?))