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