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