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