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)(11,12)(13,16)(14,15)(17,19)(18,20)(21,22)(23,24)(25,26,30,28)(27,31,34,32)(29,36,37,33)(35,39,40,38)(1,2,4,6)(3,5,8,7)(10,15)(12,19)(16,22)(20,24)(25,27)(26,31)(28,32)(29,35)(30,34)(33,38)(36,39)(37,40)(1,2)(3,5)(4,6)(7,8)(11,17)(12,19)(13,21)(16,22)(26,28)(27,34)(29,37)(38,39) involution — undirected(1,3,4,8)(2,5,6,7)(9,11,14,17)(10,12,15,19)(13,18,21,23)(16,20,22,24)(25,27)(26,32)(28,31)(29,35)(30,34)(33,39)(36,38)(37,40)(9,12)(10,11)(13,20)(14,19)(15,17)(16,18)(21,24)(22,23)(25,28,30,26)(27,32,34,31)(29,36,37,33)(35,39,40,38)(9,13,14,21)(10,16,15,22)(11,18,17,23)(12,20,19,24)(25,29,30,37)(26,33,28,36)(27,35,34,40)(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.