Love birds poop different colors? Also Can u switch a birds food?

I have a baby lovebird around 5-6 months old. I have had him for about 3 months now. I have noticed his poo is not white and green. I is either all green, red/orange and green, or a yellow and green, Sometimes it is white and green though. I looked it up and they said it could be different colors if the birds food has dyes in it. All the colors his poop has been is the color of his food. He has round pieces of food that are different colors (Red, Yellow, Green). I am no nutritionist or bird specialist but I do not think all these dyes are good for him. Expecially if his body is just ping them through. I am afraid he is getting poor nutrition and the dyes are hurting his body. Can u switch a birds food if I do the switch slowly by slowly decreasing original food and increasing his new food? Thanks