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