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