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