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