$ clisp

<...snip...>

[1]> (load "quarto.l")
;; Loading file quarto.l ...
;;  Loading file lp.l ...
;;  Loaded file lp.l
;; Loaded file quarto.l
T
[2]> (task51--uniform-color-p-demo)
((B-) [B+] [B+] (B+)) is uniform in color? T
((r-) [r+] [r+] (r+)) is uniform in color? T
((B-) [R+] [r+] (R-)) is uniform in color? NIL
NIL
[3]> (bye)
Bye.