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