star wars - Do any clones refuse Order 66?

When the clones are issued Order 66

telling them to turn on the Jedi,

do any of them refuse to carry out the order?

Answer

There's no evidence within the main film and TV canon of a clone trooper disobeying Order 66 (due to the fact that they were implanted with an "inhibitor chip" guaranteeing their loyalty).

Probably the closest we get is in the Clone Wars TV series where we meet a deserting Clone named Cut Lawquane. Since he's hiding from the Empire and supports the Jedi, I think we can reasonably assume that his chip is already damaged in some fashion and that he would have refused Order 66 if he received it.

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Elsewhere in the book EU, we see in Dark Lord : The Rise of Darth Vader that not all of the clones obeyed Order 66. An entire squad went rogue due to their affection and personal loyalty to their Jedi general

“Word has reached me,” Palpatine was saying, “that a group of clone troopers on Murkhana may have deliberately refused to comply with Order Sixty-Six.”

Vader tightened his hold on the lightsaber. “I had not heard, Master.”

He knew that Order Sixty-Six had not been hardwired into the clones by the Kaminoans who had grown them. Rather, the troopers-the commanders, especially-had been programmed to demonstrate unfailing loyalty to the Supreme Chancellor, in his role as Commander in Chief of the Grand Army of the Republic. And so when the Jedi had revealed their seditious plans, they had become a threat to Palpatine, and had been sentenced to death.

On myriad worlds Order 66 had been executed without misfortune-on Mygeeto, Saleucami, Felucia, and many others. Taken by surprise, thousands of Jedi had been assassinated by troopers who had for three years answered almost exclusively to them. A few Jedi were known to have escaped death by dint of superior skill or accident. But on Murkhana, apparently unique events had played out; events that were potentially more dangerous to the Empire than the few Jedi who had survived.

“What was the cause of the troopers’ insubordination, Master?” Vader asked.

“Contagion.” Palpatine sneered. “Contagion brought about by fighting alongside the Jedi for so many years. Clone or otherwise, there is only so much a being can be programmed to do. Sooner or later even a lowly trooper will become the sum of his experiences.”