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