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