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