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