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