Foreign driver gets a ticket in my car

If you get a real ticket with the court’s information (rather than a so-called "snitch ticket" from the camera company), you should plead not guilty by reason of identity mismatch. You cannot be found guilty or otherwise have any penalty for being the owner of the car, if you were not the driver. You absolutely do NOT have to disclose who the driver was. (If the form asks you to disclose, simply refuse to disclose; the worst outcome is you have to go to court (or do trial by written declaration, if allowed) and plead not guilty, and be found not guilty.)

In California, red light camera tickets are treated like other moving violations, which are criminal cases (i.e. criminal courts have jurisdiction). The burden of proof is on the prosecution, to prove that the defendant charged is guilty "beyond a reasonable doubt", which requires proving that the person charged was the driver "beyond a reasonable doubt". If you are charged, and the picture does not clearly show your face, the prosecution cannot prove their case, and you must be found not guilty. You don’t need to prove, or even claim, that the driver was not you, to be found not guilty — the burden of proof is on the prosecution, so it is they who have to prove that you were the driver to have you found guilty.

As the defendant in a criminal case, you always have the right to not testify in your own trial, so you cannot be forced to answer questions like, whether you were the driver, or who was the driver. (So, in fact, even if you were actually the driver, if the picture does not clearly show your face, you can still do the same thing of pleading not guilty, declining to testify, and be found not guilty if the prosecution cannot prove it was you beyond a reasonable doubt. You would not have committed perjury since you would not have testified that it was not you.)

In some other jurisdictions, there is a fine imposed on the owner of a vehicle that ran a red light camera, and the only way to escape the fine is to disclose who was the driver. But there is no such thing in California. There is no provision in California law that provides for a fine or other penalty on the owner of the car for a red light camera violation, other than on the driver who is found guilty of (or pleads guilty to) the violation.

IANAL and this is not legal advice.

A quick google of "california friend ran red light in my car" turned up a lot of lawyers websites that seem have the same basic information. This one (choose at random) states (my emphasis):

California law states that the driver cited for a traffic violation is
liable for the ticket, not the vehicle’s owner. However, if your
vehicle is captured running a red light by a red light camera, the
ticket will be mailed to your address. Thus, if you receive a red
light camera ticket in the mail but you were not the person driving,
you should hire an attorney to challenge the ticket.

and

If a friend or family member was driving your car, the Judge might ask
you to identify the person in the photograph. It is important to note
that you are not legally required to provide this information to the
Judge. A knowledgeable traffic attorney should notify you of this and
should raise this argument in traffic court. Thus, your ticket may be
dismissed and the police agency will then have the burden of
identifying the driver by matching the red light camera photo to their
driver’s license records. If the police agency is successful in
identifying the driver, they will send the citation to said person via
mail.

So it comes down to how you want to spend your money, and if you can get money out of your friend. But basically, if you want to avoid points, and insurance costs you need to contest the ticket and go to court. In a case like this I would suggest contacting a bunch of lawyers who specialize in traffic violations in California, and get an idea as to how much it will cost you. Then you can make a reasonable plan about where and how to spend your money. I would also be informing your friend about all of this and seeing how much of a "friend" they are.

Finally, Note that all these websites I saw want you to hire them. I’m not promoting any of these sites, and you should make your own choice.