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