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