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