Colour recognition in toddlers

[suzi2]

DS is 2.7 and has known most of his colours for a while. He can now do blue, green, red, black, pink, brown etc etc. But anything yellow he calls "blue". Until I correct him then if it's a familiar object, like a picture of the sun, he'll then use yellow. If it's a different style picture of the sun he's back to blue.

Is this a normal toddler thing? Or could he have some sort of colour blindness for yellow?

I think it's normal, my son knew all his colours but for ages (6 months or so) got muddled up between blue and red for ages. He's fine now!

Sounds pretty normal though worth keeping a bit of an eye on. DD did the same with red and green (she always called green red) which had us worried for a while but she got it sorted after a while.
They can't do much testing before they are 4 or 5 anyway - we were worried enough to enquire