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