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