Some people find it easier to visualise gold rather than "white", other people find "white" easier. Either way I don't think it matters if you hold the intent to visualise the light that is the highest possible vibration and that arises from The Source.

Other colours are good for specific things, which you can explore for yourself as you become more accustomed to visualisation. For example, gold/yellow is particularly good for immune function, because it relates to the solar plexus chakra. Blue/lavendar is very calming. But there's not really a right/wrong. Energy will follow your intent, so sometimes you will "try" to visualise a colour and you'll get a very different colour, because that's what's needed. Part of becoming proficient in all of this is learning to trust you own intuition about how you practice.