Purple pied kind of have all those colors.... this is my young male, doesn't have his train yet. I'd look at breeders close to you over an auction. Local town auctions can be good and bad. You can find nice looking birds and a large variety of things, and might catch a good price, but problem is that you don't know were they come from, you don't know what diseases they may have or had, you don't know what they are being exposed to while they are at the auction..... so it is a risk.... and if they have something that can spread to your other birds it might end up a very expensive risk..... but I have heard people buy nice things there.....
I would not put a 3 month old in with adults, unless you have a lot of space. Adults tend to be bossy, especially to younger birds and can really hurt them or possible kill them. It largely depends on space and temperament of the birds, but I rather be safe than sorry.
As far as finding a healthy bird - look at it's overall appearance, it should be fairly clean with in reason, eyes should be bright and clear with no squinting, no watering, no swelling, no discolor. Nostrils should be fairly clean, no discharge and no strong smell. Should hear no coughing, there should be no wheezing when you listen under the birds wing for the lung sounds. Legs should be smooth and shiny with out raised up scales, gashes or injury. no worms in poo. Should not have an off walk, hips should be equal level on back, no dipping. feet should be smooth and all pads should be with out swelling, no swelling or raised spots in between toes. vent area should be fairly clean. No real keel bone should be felt on chest, bird should be of good weight. Color on bird should be nice and shiny - dull color could indicate poor condition....
Also check how they keep the bird, dirty green water, moldy feed etc..... indicates they might not keep up with the bird.
