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