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