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