Yellow hello or hello yellow

I am trying to teach my toddler colours. He has a play mat with red, blue, green and yellow coloured squares. I take his little hand put it on the different squares and go, blue, red, green, yellow. Sometimes when I say red he will say 'd' only with a lot of emphasis and it comes out like ddh, ddh. So far so good.

But when I say yellow he immediately puts his palm against his ear.

In his understanding yellow and hello are the same. And he is used to seeing his parents do a lot of hellos over the phone. So for yellow he walks around with his hand against his ears and a big smile on his face that says, 'I get it Amma.'

The other day we were in the lift with another gentleman who smiled brightly at my toddler and said 'hello!'

My son immediatley put his palm against his ear and smiled at me and at the gentleman.

And I went into translation mode...