What is are the numbers for these color combinations?

Using the RBG color model, what combinations of red, green, and blue should be used to achieve these colors in between red and blue?

Red is (255, 0, 0)
Blue is (0, 0, 255)

I also need to create:

- 50% red, 50% blue
– 75% red, 25% blue
– 25% red, 75% blue

For 50% red, 50% blue, do I make it (255, 0, 255) or, like, half of each, as in (128, 0, 128)?