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