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