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