How long has it been in the pot? and when did you last feed it? They prefer an acidic compost [ericaceous] . you can buy a specific feed for rhododendrons/Camellias from the garden centre. You could also give it a dose of Epsom salts. 1 teaspoon in a litre of water. the lack of green pigment could be due to lake of minerals mainly magnesium and sometimes boron.
it is usual to find the odd leaf going over as they shed the old leaves bit by bit all year.

It has been in the pot approximately 3 yrs ,it is in acidic compost and I have feed it with specific feed. Also it as never flowered since I purchased it. I will give it a dose of Epsom salts and see what happens.Thanks for. advice

do you give it plenty of water through the summer as this is when the flower buds form? perhaps it is time to move it up a size in pot also. do you have a suitable space to put it in the ground. they are 'happier' with a good root run.

It also looks like it might have zinc deficiency. Is a bit of zinc a part of the "specific feed"? It does look like it could use a bigger pot.