Is it ok to change just one tyre?

Hi there,

My front left tyre has a 1cm cut at the side so I'd like to change it. It says it's a Formula Gti 155/70/R13. Tried searching for another Formula tyre but couldn't find it (does it exist?). Is it alright to stick a different brand tyre like Toyo instead? Which would mean the back two tyres are the same but the two front tyres aren't...

Ezra
August 2006