Hi everyone, I may be opening a can of worms with this question. Do you think Ultramarine Blue is a warm or cool blue ? Until now I believed it was a warm blue because it had some red in it, which warmed it , thus making it a warm colour. I was giving a short talk at our local Watercolour Art Group recently, the title was " properties of colour" and I decided to do some research. what an eye opener; contrary to what I had previously learned and read, Ultramarine blue was considered a " cool blue". Cooler than " Phthalo blue which was considered a warm blue, because it had more yellow in it than Ultramarine. It has got to do with the colour wavelengths..... one of the blogs I read was by Sharon Hicke. @ sharonhicksfineart.com. Just google Ultramarine warm or cool, you will find it. I brought the subject up because I am currently reading " The elements of landscape painting " by Suzanne Brooker. Anyone want to comment ? I still look at her colour charts and see " warm"