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