There are many reasons which require a go-around or missed approach. These may be technical due to a system failure or more practical like not being able to see the runway.
The conditions you describe, if this was a heavy rain shower, suggest perhaps wind shear, a sudden change in wind strength and or direction. This may cause the aircraft to deviate from the correct flight path causing a situation known as a non-stabilized approach. This requires a go-around. Such is the nature of the weather that the next aircraft may not be affected in the same way.
Incidentally, I had a gliding instructor who was completely colour blind. Also, the new National PPL has a more relaxed medical requirement. Check it out you may get a licence after all.
Hope this helps.