How Would You Try to Accomplish This?

My cousins adopted two girls from China.

They are both blind.

Both are thriving here in the states.  Both have learned braille and one of them has won an award for three consecutive years for most books read in braille. 

But my aunt (the girls' grandmother) told us of a difficulty they are running into.

"How do you teach these girls the concept of colors?" she asked.

Of course, being blind from birth, they have absolutely no concept of what it means to have color.  Green means nothing.  Blue means nada.  They are simply words pulled out of thin air for all these girls are concerned.  For a shape, they can create a triangle and have them touch it.  For an object, they can find that object and have the girls feel it.  How do you do such a thing with something intangible like a color.

It set my mind reeling, not only with the practicality of trying to do such a thing but also with a theological question:  how does one convey the concept of God to someone who doesn't believe?  How does one convey the concept of something one cannot see--that cannot be grasped--that cannot be felt or touched (at least until one believes)?

How would you seek to convey such a concept to one who could not see?