By selecting a connector in the browser while in the Asset Builder, the color gets selectable. However, it doesn't stick to it if the asset is published or the AB is closed.
I see huge value in different colored connectors to ease up the progress of making layouts. Many different people are making layouts in my company, but usually none of them are making the assets.
Then an extra step might be taken and we can only connect blue+blue, green+green, yellow+yellow etc.