I'd have to say the depth at which Red, or any other color starts to
disappear is based on water clarity. If the water is gin clear, you'll
be able to see red at 10' or more. If the water is muddy, you won't see
it even a couple inches under the surface. According to Keith Jones
(Berkley's lead scientist), Bass (largemouth) can see distinct colors
very well in a certain color range, including red. Red, like purple,
dark blue, and dark green will all turn "black" as light penetration
becomes minimized. Walleye on the other hand can see into the infrared
spectrum, where (allegedly) bass cannot. The exceptions to the color
rule of course are the fluorescent colors, they will hold their colors
with less light penetration.
In my opinion, the concept of red line being invisible is a joke. I
believe I used to watch Doug Hannon use a sharpee and color blocks of
his line with the marker, so every so many feet you would have a black
line. It looked pretty cool with underwater footage, but we have
fluorocarbon now, I am a HUGE fan of fluorocarbon :-)

Chris
johnval1 wrote:
While I was in the reading room perusing the latest issue of BassMaster, and
having read every article 2 or 3 times, I noticed the Shakespeare ad for
Cajun Red line. The ad states the advantage with this line is its
invisibility, particularly after 3 feet of depth where the fish cannot see
the line. This is due to the water filtering out red on the lower end of
the light spectrum, rendering the line more or less invisible to fish. OK,
this makes sense to me, sort of.

I must have half a dozen crankbaits of various sizes in red, most of which
run a depths greater than 3 feet. I have caught good numbers of fish on
these red cranks. Now, how in the hell is this possible if the bait is
mostly or entirely invisible to the fish? I must be missing something in
this equation.