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