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