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