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