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