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)(27,33)(28,38)(29,34)(30,35)(31,32)(36,37)(39,40) involution — undirected(1,2,5,6)(3,4,7,8)(11,17)(15,21)(18,23)(22,24)(26,32)(30,34)(33,38)(37,40)(2,6)(3,7)(10,14)(15,21)(16,19)(22,24)(25,27,31,28)(26,33,32,38)(29,39,35,36)(30,37,34,40)(9,10)(11,15)(12,16)(13,14)(17,21)(18,22)(19,20)(23,24)(25,28,31,27)(26,33,32,38)(29,39,35,36)(30,40,34,37)(1,3)(2,4)(5,7)(6,8)(9,11)(10,15)(12,18)(13,17)(14,21)(16,22)(19,24)(20,23)(25,29,31,35)(26,34,32,30)(27,36,28,39)(33,37,38,40)(1,4)(2,3)(5,8)(6,7)(9,12)(10,16)(11,18)(13,20)(14,19)(15,22)(17,23)(21,24)(25,30,31,34)(26,35,32,29)(27,37,28,40)(33,36,38,39)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.