No idea but is it still the case if you disable all overlays (there is a button for that in the top menu bar of the 3D view)

the material preview mode generally uses pretty neutral world texture for lighting (some foresty HDRI image).

is your scene set to use some blue world material (or blue texture in the material?), eg. using the sky texture node which is cranked to very high emission strength?

edit: or have you perhaps accidentally made your sun -lamp blue?

hiro8811 might be right about blue light object.

try this...

• add new object, maybe monkey (2m default size, no material)
• disable other objects both eye and camera icon or just delete them from the scene, one by one until it stop being blue
• if the monkey is still blue then it's something in the world material or render settings or compositor

The light that loads when you start a new project. I just think of it as “the sun” because it not a directed light a spotlight.

The sun... IRL behave like a point light so you are technically correct XD
The "sun" type light is there so you don't have to move point light 149,597,870 km away from your scene center (you can't and it will break blender)

Because...it's...gay. Love and support it.