Often when planning a new paint scheme you will have a series of colours in mind but are unsure which exact variations of the colours to use. This can be problematic if you don’t have the time or ability to do repaints if you don’t like the chosen colour choices (some resins can be difficult to strip paint from and multiple paint layers can quickly obscure fine detail).
To solve this dilemma I use plain white index cards to trial colour swatches to help me select from the possible colours. Even if you don’t ultimately use any of the colours always keep these as you may use them for a future project.
Here we see a card I did some time ago but didn’t use that I’ve now resurrected for another project.