One vertex per element, one color per generator, with an edge from x to x·s.
(2,5)(3,7)(9,10)(11,21)(12,19)(13,18)(14,17)(15,20)(16,24)(22,32)(23,37)(25,31)(26,40)(27,34)(28,33)(29,36)(30,39)(35,38) involution — undirected(1,2,4,5)(3,6,7,8)(9,11,13,24)(10,16,18,21)(12,26,27,38)(14,25,15,22)(17,32,20,31)(19,35,34,40)(23,28,39,29)(30,33,37,36)(10,17)(11,22)(14,15)(18,20)(19,33)(23,38)(24,25)(26,39)(28,29)(31,32)(34,36)(35,40) involution — undirected(1,3,4,7)(2,6,5,8)(10,18)(12,27)(16,21)(17,20)(23,39)(26,38)(28,29)(31,32)(2,5)(6,8)(9,12,13,27)(10,19,18,34)(11,23,24,39)(14,28,15,29)(16,30,21,37)(17,33,20,36)(22,38,25,26)(31,40,32,35)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.