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