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