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)(11,15)(12,26)(13,24)(14,20)(16,21)(17,22)(18,30)(19,33)(23,32)(25,34)(27,28)(29,37)(31,38)(35,40)(36,39) involution — undirected(2,5)(6,7)(9,11,15,10,17,20,14,22)(12,27,30,36,32,38,29,40)(13,24,16,19,34,25,33,21)(18,28,26,35,37,31,23,39)(9,12,15,30,17,32,14,29)(10,18,20,26,22,37,11,23)(13,28,16,35,34,31,33,39)(19,27,25,36,21,38,24,40)(1,3,4,8)(2,6,5,7)(9,13,15,16,17,34,14,33)(10,19,20,25,22,21,11,24)(12,28,30,35,32,31,29,39)(18,27,26,36,37,38,23,40)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.