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