The leaves on your Bird-of-paradise plant are turning yellow in color probably because there's a drainage problem. If the plant is potted, check to see if there's a lot of water sitting on the soil. Only water the plant when the soil feels dry.
Could be a drainage problem , or it could be out growing it's pot . Depending on where you live , the cold affects them a lot ! They like sun and warmth . Ours are just starting to come back from Winter . They are a tuber plant , so some Miracle-gro plant food once a month helps them a lot !