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