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