Could two photons collide?

The short answer is yes, they can, but it is extremely unlikely.

Photons are quanta of electromagnetic waves. When you turn on a light bulb, it starts producing billions and billions of these particles that whizz through your living room at the speed of light. They're pure energy. They have no rest mass. Photons are a type of quantum particle called bosons. These particles are not subject to the Pauli Exclusion Principle. This means that multiple photons can be in the same quantum state and not interfere with each other. If they collide, they'll pass through each other like ghosts.