It shouldn't be yellow if it started out red, that would suggest ill health or possibly its dead. A photo would be helpful, but failing that, how long's it been in the same pot? These plants increase sideways at the root, so in pots, its necessary to turn it out, cut the rootball in half and pot up the two halves separately, or throw one half away, and this needs doing on average every other year or 3 yearly, depending on size of pot. If you've not done that and its been in the pot more than 2 or 3 years, do it now. Use new, fresh potting compost, preferably John Innes No 2 or 3, but multi purpose will be okay if not.

Its going to be hard getting it out of pot its huge .Its in a huge pot and has been in it for 3 years.May wait and cut it right back later in year then attempt to remove it.Thanks for your advice.