It's all colours and shapes. So whatever I hear, smell or feel gets translated into a visual impression with a colour and a certain shape. Smells are more colours and less shapes (it's more a texture there for the lack of a better word), where as any sound or all pieces of music have a distinct appearance. All letters have there own colour, but this is formed by how the letter is pronounced. Pronouncing H in my native language is more yellow-weight, whereas in English it's more greyish. Days, months and years have their own colour, so when talking about making an appointment, I automatically visualise a timeline where the appointment gets scheduled in.

It's honestly quite fascinating. A music teacher of mine hypothesised once that I might have perfect pitch, and indeed it took me only little effort to identify sound (intervalls and single notes) on a piano. But then again I don't have any feeling for rhythm and can't sing at all, so there's little use to that...