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