PUZZLE 090 Colour Confusion

This square has been divided equally by diagonal lines, and each of the sections has been painted a different colour.
The top is red, the right is yellow, and the bottom is blue.
Apparently, when the left section is painted, it will be a larger area than each of the other three colours.
What colour is the left section?

Hint 1

The outside of the square is irrelevant.
The answer is there within the square.

Hint 2

The area of each of the triangles is the same, so you need to increase the size by looking elsewhere.

Hint 3

The lines inside the square are quite thick.

Super Hint

If you paint the section the same colour as the lines, its area will increase by the size of the lines.
The lines are black.

Answer for 'Colour Confusion'

The answer is '6'.