What this project is basically explaining to you is that daylight changes colour during the day plus also as the weather conditions change, for example
On a cloudy day as above the light appears white and quiet soft, the light will also appear white around the middle of the day dew to the angle of the sun. The reason the cloud cover makes the light appear softer is because it acts as a natural diffuser much like the ones used in a studio set up that you place in front of the light source.
Next the light can appear blue when the sky is completely clear or between sunrise and midday and midday and sunset depending again on weather conditions.
Finally daylight can appear orange at sunrise and sunset, this is coursed by the angle of the light reflecting off the cloud cover or by the amount of dust present in the atmosphere. The colour can range from orange to red depending on the conditions again meaning that if you understand the weather conditions you can get yourself in the right position to take advantage and get the right results.
Another point to be aware of that isn't mentioned in the course material is that with modern photo software such as Photoshop you can easily add colour filters to your work meaning it isn't always necessary to buy expensive colour filters because its now possible to alter the colour cast in post production. I know alot of the older generation of photographers would argue that this isn't the best way to get the right results but when I've experimented with the two different processes (using a colour filter and adding one in photoshop) i personally can't see to much different. I supposes it just matter of preference on how you like to work.