What is a Warm or Cool Colour?

A warm or cool colour is determined by how far away it is from the 'hottest' and 'coldest' colours on the colour wheel. The hottest colour is considered to be a red/orange (tertiary colour), and the coolest is the opposite of this (complementary colour), which is a blue/green. 

This means that defining a colour as hot or cold is always down to the context of the other colours. While red/orange is always the hottest and blue/green is always the coolest, all the other colours are affected by the other hues around them.

Having a colour wheel will help you so much with warm and cool colours. Download this free PDF workbook with 8 different colour wheels inside.

How to work out if a colour is hot or cold

For example, if I have purple and green but no other colours, purple is warm and green is cold. How do I know this? Because green is closest to the cold axis of green/blue and purple is closest to the hot axis of red/orange. 

However, if I then added red into this mix so I had purple, green and red, purple is no longer the warmest colour. Red sits closer to the hot axis of red/orange than purple. So, red becomes the warmest colour, green remains the coolest colour as it's still the closest to green/blue and purple becomes a neutral colour, equidistant from the hot and cold axis. 

How can I have a cool red and hot blue?

Ergo, if colour is all about context, we can have a hot blue and a cool red. Let's take red to start with. The colour family (hue) or red has a range. It becomes a bit pinky/purple before changing colour to purple and likewise can be a bit orange before changing over to orange. This gives red a spectrum from red/orange through to red and then red/purple. 

We know that red/orange is the hottest colour, always, so red/orange is the closest to this axis...well it is this hot axis! That means as we move to red, we are getting further away from the hottest point and moving towards the cooler axis. So, in the world of red, we have a hot red that is red/orange, a neutral that is just red and a cool red which is red/purple. 

Remember that this is the case only when we have the hue of red and nothing else. If I were to change things up and take the 'cool' red of red/purple and then use blue/purple and nothing else, suddenly red/purple wouldn't feel cool anymore. In this scenario, without red and red/orange around, red/purple is the closest colour to the hot axis and blue/purple is closest to the cool axis. 

Use a Colour Wheel to Help You

Download the free PDF colour wheel bible

If you're struggling to remember the order of the colour wheel and can't visualise which colour is closer to the axis, then download this free colour wheel book. You'll find 8 different colour wheels inside to help you with all things colour theory.

Mark on the hottest point (red/orange) and the coolest point (blue/green), stick it to your wall and decode your colours. It's just a game of closer or further away, that's all it is. Remember that when a new colour is added, you need to stop and consider if this changes the balance of your palette. You may have shifted the temperature gauge around!