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