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