Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I’m double, I’m single,
I’m black blue and gray,
I’m read from both ends,
And the same either way.
I sometimes come in a can but I'm not food.
I sometimes come in a bottle but I'm not a beverage.
I come in different colors but I'm not a rainbow.
I'm sometimes used with canvas but I'm not a tent.
I'm used with a brush but I'm not toothpaste.
What Am I?