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