Getting the right colours for your photographs is a question often posed to me by photographers. Doing it at home after the shoot is fraught with dangers. It is impossible if you shoot jpg, and requires a well trained eye to get right in post production
There are a few things you can do while at your shoot to make this easier.
Possibly one of the easiest is to use a grey card or even a white sheet of paper. Be warned not all white paper is created equal. Paper has different colours (hues) and tones. Each is unique and whatever colour it is, it will be introduced into your photographs. Therefore it is best to purchase a neutral source such as a grey card.
To get your colours accurate choose a neutral white via a specific tool. Expodisc and Colour Passports are two such solutions.
Finally there are instruments which measure the colour temperature, though these have lost out in popularity with digital cameras as we no longer use colour correcting filters while taking photographs like we did with film.
The expodisc is quite simple to use
The colour passport gives you a lot more control
Adjusting your white balance in Lightroom
How to make selective changes to white balance