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