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