You will need a JAR Class 2 aviation medical and I have copied quote from there site.
Colour Vision
You will be tested for normal colour vision with Ishihara Test Plates. If you fail these you can still gain a Class 2 certificate, but it will be limited to flying by day only. This limitation can be removed if you pass the Colour Assessment and Diagnosis (CAD) test. If you wish to take this test, you should contact the CAA Medical Department, Gatwick, to get details of the nearest facilities to you.