A white light, as we all know, is composed of seven lights VIBGYOR. Each of the component lights has distinct frequency ranging from one value to another. So, when the photons have wavelength of 600 nm it becomes a yellow light and when it changes to 700 nm it becomes a red light. So, does this imply that the frequency with which a group of photons vibrate determine the colour of light? Well, in that case, with what frequencies are photons vibrating for a white light?
To get a perception of a white light, one has to observe simultaneously many photons having different frequencies and obeying a certain distribution function.
Keep in mind that a color is not a physical property, since it is resulted from human brain's interpretations of signals coming from eyes receptors.
Light that our eyes, or other system of detectors, would perceive as "white" could have several different maekups:
It could be a stream of photons all in different energy / momentum eigenstates. That is, there could be a population of photons, some of which are red wavelength, some blue, some green and so forth as in freude's answer; OR
It could be made up of photons all in exactly the same quantum state. You really can have one, lone, sole "white" photon all on its own. A photon, like any other quantum object, can be in a pure quantum superposition of basis eigenstates (eigenstates of whatever observable you care to work with). There is no reason why a photon has to be in a pure energy / momentum eigenstate. Its state could be such that there is a complex amplitude $\psi(\nu)$ to be observed at wavelength $\nu$. For more information about this idea, see my answer to the following question How can we interpret polarization and frequency when we are dealing with one single photon?