Blood in droppings can also affect the color of the poop... which is why I advise against colored pellets. I've also noticed firmer, healthier droppings when fed a dye-free pellet vs a dyed pellet - even if it was just the difference between Zupreem Fruitblend and Zupreem Natural. (I would recommend Harrison's, TOP's or Roudybush as best pellets, though)
Is feeding pellets the same as feeding fresh foods? No it's not! Pellets are "dead" foods. Fresh foods and sprouts are *living* foods. They have enzymes in them.
Pellets are essentially processed food. It's been proven that humans do better on *fresh* foods over processed foods. Dyes, preservatives and the fortifying of the foods is not that healthy... when they fortify something, they may use synthetic vitamins or even using *part* of the vitamins themselves rather than the whole vitamin.
Now, I'm not saying that pellets are *bad*, because they are a huge improvement over seed diets! I'm just saying that *fresh food* is best! I often recommend pellets because it's not always easy to provide a proper fresh food based diet to our birds. Yes, fruits and vegetables are healthy, but where's the protein? Eggs can provide protein, but should be fed in moderation... and when fed as such, do not provide enough protein to make up for the amount of protein lacking in fruits and vegetables. Grains and legumes do. Quinoa is a "superfood" because it's a complete protein! Otherwise, one part legumes (*healthy* ones I would like to stress) to two parts grains can also make a healthy "complete" protein.
Ya, seeds are bad! Seeds are unhealthy! Not quite true... Remember, things in moderation. Some seed is fine! Better yet, sprout it! Then it's awesome! It's alive! It's fresh!
As far as a pelleted diet vs a fresh food diet... I have heard of breeders who fed pellets and had healthy birds... then they switched to a fresh food based diet, and the birds health improved and they had more offspring! Likewise, I have heard the opposite said!
It honestly varies... and it may depend on what foods are being fed and in what proportions.