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