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