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