JK
IMHO, I believe there are bigger issues than the visibility of braids when using them for drift fishing. They are abrasion around rocks, retying good knots and the ability to break off when snagged. But the good news is that you can solve these problems and visibilty too by simply adding a short section of monofilament to the end of your braided line. This often referred to as a shock tippet and is very similar to using a leader off a fly line in flyfishing. This short section (2-4') of mono can be whatever suits your situation best, like low vis, high abrasion, stiff, soft, high test, low test, green, dark, clear or whatever. Then you can retie good knots easier and break off at the terminal end instead of leaving braid in the river. As far as connecting knots between braid and mono, I have found the double-uni to be the easiest and most secure connection. Hope this helps.