

I get it why Taekjoo's a bit white/paler
it's because he's on his winter shade. There's summer shade and winter shade. Winter shade skin which is where your natural, untanned skin tone after minimal sun exposure means your skin would be lighter and have cooler undertones. Meanwhile summer shade skin is your natural tanned or sun-exposed skin tone means your skin will be darker, often warmer/golden undertones.
In short, summer skin is typically 2–5 shades darker than winter skin, depending on how easily people tan. People often have two shades of skin, for winter and one for summer.