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