I have tried to come up with an appropriate thing to say, when I need the children to come to the mat. I'm not keen on the old usuals, "one two three, look at me", etc. I wanted something that was right for the art room. The following little chant is working a treat.
I start at one colour on the colour wheel and slowly go around until I am back where I started.
"Red, orange, yellow, green, blue, purple, red."
The children soon start helping me.