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