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