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