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