At a guess you either lost or had a lower power than required colour signal. Most probably it was the green colour signal, as blue and red were still in evidence.
White is composed of the 3 colours used in TVs (and monitors etc., i.e. red, blue, green) being all on at 100% power at the same time.
All the colours produced in a TV are made up of the 3 colours, having various power percentages, in relation to each other at the same time. e.g. 35% red 50% green and 80% blue will produce a slightly different colour to 40% red 45% green and 75% blue.
There is a lot of information online on how the colours are combined to form the required colour.
Given that the problem was 'solved' by what was effectively a "power reset", as most TVs nowadays are software controlled, either some software was stored corruptly or perhaps the components that apply the colour signal power might not have had the correct power applied to them at that time etc. There could be a myriad number of reasons as to why it occurred
As it was intermittent, at the moment you can only wait to see if it happens again and then hopefully if it actually stays that way. With the problem in evidence all the time it will be a lot easier to track it down. Initially, you could try unplugging the TV from the power and removing the back off it and do a visual inspection of the boards and connectors, especially the power board, for anything obviously amiss such as bulging capacitors or stressed (heat affected) components or anything loose, but this may prove inconclusive if it all seems OK.