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