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