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