Please use whatever you like to create.

A few ideas below:
Watercolours
Acrylics
Mixed media - with pastels, collage, paint, photography etc

My favourite paints are Golden Fluid Acrylics - I like their intensity, as well as their ability to water down like watercolours. Their flexibility is great for experimenting.

You can paint on paper, canvas, board - anything that you have at your disposal.

Have fun!