One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,8)(3,6,7,4)(10,11)(15,17)(16,18)(23,24)(25,26)(27,31)(28,29)(30,32)(33,37)(34,35)(36,38)(39,40)(1,3,5,7)(2,6,8,4)(9,10,14,11)(12,17,20,15)(13,16,22,18)(19,24,21,23)(25,27,30,36)(26,31,32,38)(28,34,33,39)(29,35,37,40)(1,4)(2,7)(3,8)(5,6)(26,32)(28,33)(31,38)(34,39) involution — undirected(1,3,5,7)(2,6,8,4)(9,11,14,10)(12,17,20,15)(13,18,22,16)(19,24,21,23)(25,28,30,33)(26,29,32,37)(27,34,36,39)(31,35,38,40)(1,4)(2,3)(5,6)(7,8)(9,12,14,20)(10,15,11,17)(13,21,22,19)(16,24,18,23)(25,27)(26,31)(28,34)(29,35)(30,36)(32,38)(33,39)(37,40)(1,2)(3,6)(4,7)(5,8)(9,13,14,22)(10,16,11,18)(12,19,20,21)(15,23,17,24)(25,29)(26,33)(27,35)(28,32)(30,37)(31,39)(34,38)(36,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.