In the photo, below, there are several areas that we would usually call, "white". Let's look beyond the
family resemblance by comparing the whites to each other.
The barn in the background has white siding and a white roof. Do you agree that the siding is cooler than the roof? To me the siding looks practically blue in comparison. So, It's fair to say that the roof of the background barn is warmer than the siding.
Now compare that roof to the siding on the closer barn. Which is warmer?
Hopefully, you can see that context invites comparison. How warm is the roof on the background barn. Compared to what? It's warmer than the background siding but cooler than the siding in the foreground.
It's sometimes difficult to keep track of whether we're comparing color temperature or value. Look at the truck in the foreground, for example. The potatoes are definitely warmer than the sky, but are they lighter or darker? Let's take the color out of the equation:
When we're just looking at value the potatoes are very similar to the sky, closer than you may have thought.
For homework, pick two colors, one warm in comparison and one cool. Use the white barns picture or one of the following ;
I would change the color of the yellow car. It's too similar to the yellow building and they get tangled up together
Identify the warmest thing in the picture and paint that with your warm color in its pure form. Find the coolest thing in the image and paint that with the pure form of your cool color. The second warmest thing will be your warm color with a little bit of the cool mixed in. The third warmest thing will have a little more of the cool mixed in. Do you see where this is headed? It helps to read it a couple of times. Although the exercise is about color temperature you still have to get the values in the ballpark. There will be lots of comparing.