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