26 mths is quite young to diagnose colour blindness. It could be that she probaby doesn't remember the names of the colours and calls them any name that comes to her head. Girls are unlikely to be colour blind, they carry the gene and pass it on to their sons who are affected by it but can't pass it on.

Is she getting particular colours like red, green, yellow or brown mixed up? These are the ones that usually get mixed up by colour blind people.

My brother is colour blind, he had a lot of trouble with colours as a child but it was never thought that he could be colour blind. It wasn't until he was at school that a teacher picked it up. Because my brother is CB I coudl be a carrier so I had my Ds was tested when he was in kinder and he wasn't colour blind.

You could take her to an optometrist for testing but she is quite young and probably wouldn't understand the test. She is only young and will probably pick the colours up in time, if she doesn't definitely look further into it.