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