Excuse me if this question has been asked before.

I do most of my fishing for sea trout and the general opinion of a lot of experts seems to be that sea trout see colours more as shades of grey/black than distinguishing the actual colours themselves, so the size, speed, depth and silhouette of the fly are more important than the colour as an attractor.

I undertook a small and admittedly unsophisticated experiment at my local stillwater where I fished with black, red and olive tadpole patterns for 20 minutes each using the same intermediate line and speed of retrieve in the morning and caught two rainbows with each pattern in that time.

I have sort of concluded that in this instance the colour wasn't so important, rather it was the size,depth and speed of retrieve that were the main factors.

I have no great expertise or experience in this area and I wondered what were the views of some of the more experienced anglers on here on whether rainbows are able to differentiate between colours.

Cheers

Not sure about using lures for the experiment. They're suggestive stimulus at best so their colour is less critical I'd say.

Try it when the fish are preoccupied on a particular food source and you might have different results.

I really hope they do, otherwise I've got about 20 times as many tying materials as I really need!

Its generally accepted that they see aspects of light where by they can distinguish certain colours, their eye receptors see flash and types of darker shades,

I am going to say something which I expect some expert to come along with superior knowledge and contradict.
But its the difference between the visuals of sea trout and ordinary browns/rainbows. (this is based on the accumulation of various things i have read, and not quoted from one source).
The trouts eye differs from ours in terms of the regulation of amounts of light entering the eye and landing on the receptors at the back of the eye ball; the rods and the cones.
(Remember this bit and the rest is clear) The cones deal with colour information and the rods deal with density of colour or contrast.

All this info is fed into the optic nerve and made into an image in the brain.

Now in your eye, should someone turn another light source on in the room, the pupil will go smaller like the aperture in a camera lens, thereby restricting the amount of this light reaching the cones and rods. And by doing this the cones and rods operate at optimum and colours and contrast remain relative in all light levels.

And heres the big HOWEVER.

In fish the pupil (iris) size is fixed. So there is differing amounts of light falling on the cones and rods.
How come its not dazzled by Bright sunshine or blinded by the onset of dusk? (being a Seatrout fisherman at night you know that's not the case!).
The Rods, (that pick up contrast and density remember) adapt instead. As the light levels fall they lengthen allowing more surface area to receive light information, and Contrast becomes more dominant in the information fed to the brain.
In brighter weather the the rods contract meaning that the cones are sending more colour information to the brain.

So fish operating at night or in murky conditions are dealing with contrast and density.
Fish operating in clear waters in the light are dealing with colours and hues.

.........................................................I think!

Ps re your experiment Red is the first colour to be filtered out by water so after a certain depth red becomes Black
(un-helpfully I cant remember what that depth is.)

All i know is that their receptors analyse light and through this can determine bright and dark colours and flash,

Hobble I was writing that unaware of your posting, I am not contradicting you. Your absolutely right.

Not a million percent certain but i think blue/green black and variants of those colours, and flash which is coloured light reflecting off a reflective object

I believe this statement is more to the point "
All this info is fed into the optic nerve and made into an image in the brain.
We may understand colors but how they are percieved by the trouts brain is outside our knowledge we can only guess how a trout interprets it by the make up of the eye
Our eyes are only instruments for the brain to interpret an image , hence why some people believe they have seen ghosts

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Ok if thats what you think as regards the ghosts, what about the ghosts that speak, whats that got to do with the eyes