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