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