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