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