Why are the term MENTALLY HANDICAPPED,WHEELE CHAIR BOUND AND COLOURD discriminatingand what are the alternative words which should be used

No matter what Politically correct words rights advocates come up with the words still end up being seen as Politically incorrect and the 'handicapped' people are not the ones complaining.
They went from handicapped to disabled to physically challenged to special needs.
Personally I do not think we need the language police and that they just must not have anything better to do with their life than looking for things that offend THEM and come up with something more pleasing to their ears.

Good question. I don't know where as a society we are going with these shifting terms for individuals. If these are discriminating, the older ones were down right mean.

First, I believe as groups that have a beef with society in general become more politically active, one way to show their strength is to not allow others to name them. Colored > Black, etc. These days everyone wants to be politically correct (PC), so usually, the terms to describe these individuals are changed to meet their desires.

I don't know what is PC these days for Wheelchair Bound, but it is likely to change.

Maybe Mentally Handicapped >Special Needs... I think they are called "Special" as in Special Olympics.

I think Lenny Bruce had the right idea.