Say to your class:

I have a handkerchief in my pocket but I won’t disclose to you what color it is.

Have an other classmate be your accomplice and have him say:

Oh please, PLEASE disclose the color of your handkerchief.

Do this back and forth. Then finally pull out a RED handkerchief.

And say:

Ok, I’ve disclosed the color of the handkerchief.

Note that in the preceding, you’ve created a little play. You’ve got someone else in the class involved. And you’ve used the visual sight of the handkerchief to reinforce the meaning.

(Of course you might use a sock of something, too)

And for a real kicker, wear red that day and wind up by saying:

Yes, red is the color of my clothes, and the handkerchief that I’m here to disclose!

(And if you’re not wearing red that day, you might point out someone in the class who is.)