I like a cheddar to be yellow to the point of almost being orange. It's what I've become accustomed to from commercial examples and in my mind's eye that how it's supposed to be.
Because of that I use an 1/8 tsp. in a 4 gallon batch and find that the color is just about right.
Of course this does not at all affect the color or the texture of the cheese. It is simply there for looks.
On one hand, this should probably not even be important to the home cheese maker. On the other hand I think we are products of our environment and expect our food to look like what we are used to.
Case in point is some green ketchup my wife once bought for the kids. They loved it, because they are weird.
I on the other hand could not eat it since it did not look like what ketchup is supposed to look like.
It might be a little strange but cheddar has to have that yellow orange color as far as I'm concerned.