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