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