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