1- When you buy birds ask what they are and don't buy them unless you can know
2- Young chicks are hard to determine since they are so young and there are plenty of breeds at that age that look the same. Chicks will show feather legs and the crested breeds will start to develop a crest
3-When the bird goes through it's first molt (there are three official ones before it becomes an adult) sometimes the color will change out from the original chick color. Some chickens have exclusive varieties
4-Combs can also help some chickens (or most) have Single Combs, some have Rose, others Pea combs, and some Strawberry. A young cockerel will show more features of combs and color
5- When all else fails look in the APA standard of perfection. Breeds have defining features that make them their own breed (The standard of perfection will not accept a breed that is so simalar to another one like the example: White Java's were in the Standard but when the White Plymouth came in it was removed because there were no features that separated them) American breeds tend to be big with yellow legs.
3 of them are showing more of a comb but that doesnt necessarily mean their cockaroos right? Im so new to chickens apologizes in advance. But I do believe their done molting and their colors are permant...their about 11wks old