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