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