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)(11,17)(12,20)(13,14)(15,18)(16,21)(19,22)(23,24)(25,26,31,33)(27,35,29,32)(28,34,38,30)(36,37,39,40)(1,2)(3,5)(4,6)(7,8)(9,10)(11,15)(12,16)(13,14)(17,18)(19,22)(20,21)(23,24)(25,27,31,29)(26,32,33,35)(28,36,38,39)(30,37,34,40)(10,14)(11,18)(16,20)(19,24)(26,33)(28,38)(32,35)(36,39) involution — undirected(9,10)(11,15)(12,16)(13,14)(17,18)(19,22)(20,21)(23,24)(25,28)(26,34)(27,36)(29,39)(30,33)(31,38)(32,40)(35,37) involution — undirected(9,11,13,18)(10,15,14,17)(12,19,21,24)(16,22,20,23)(25,29,31,27)(26,35,33,32)(28,39,38,36)(30,40,34,37)(1,3,4,7)(2,5,6,8)(9,12)(10,16)(11,19)(13,21)(14,20)(15,22)(17,23)(18,24)(25,30,31,34)(26,28,33,38)(27,37,29,40)(32,36,35,39)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.