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