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