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