Primary colours are red blue and yellow and you mix combinations of them for new colours!!
Red is a primary colour and although it is one of the colours used to create secondary and tertiary colours and shades it is not possible to mix other colours to achieve a true red.
Red and orange
you get purple
red and brown
red and yellow
you can mix the colours red and blue
Red is a primary colour, that means you can't get it by mixing other colours, it is one of the tree basic colours.
to get a tertiary colour you have to mix 2 primary colours. primary colours are red, blue and yellow.
dark green
Brown
Red is a primary colour. It is one of the building blocks of colour. This means you can mix other primary colours (blue & yellow) to it to achieve secondary and tertiary colours, but you can not mix other colours to achieve red.