I received a traffic ticket for holding my cell phone in my hand while on speaker phone. Am I able to contest the ticket?

Of course you can, but don't plan on winning.

If the law prohibits HAND HELD phone use, you ARE guilty of violating the law. Putting the phone on speaker isn't the issue. HOLDING the phone in your hand is the violation.

The ACTUAL WORDS of California law are HANDS FREE. You admit you WERE using your hand to hold the phone instead of the steering wheel.

No, you seem not to understand the term "Hands off".

You can contest all you want. Will you win? Unlikely.

That depends on your state/local law.

"I've read that if it's on speaker phone you can contest the ticket. Is that true?"

You can contest, but you will lose. If this claim was to be allowed in the law, then EVERYONE would immediately make the claim. And escape the ticket.

That's wishful thinking.

Pay the fine and keep your hands off the phone from now on.

What is the law in your state? I have seen people holding cups of coffee in one hand while driving.

It depends on the laws in the state in which the violation occurred.