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