I sometimes describe colours as being really warm or only mid warm or even just a little warm and I’ve been asked to share some pictures so you can see the differences.
In this picture I’ve taken three colours and moved them from the really warm through the mid warm, via a little bit warm to a little cool and onto medium cool before ending at really cool.
Can you see that there is more yellow making up the colours in the garments on the left of the picture, whilst more blue in the ones on the right?
The problem with the early seasonal colour systems is that they took all their colours from the extreme right or left as far as undertone went, rather than having options for people who are closer to the warm/cool divide. There are many people who are less obviously warm or cool, and they struggle figuring out where they sit within any of the less nuanced colour systems.
You may also find this post on undertones, colour and ageing useful.