The question of colour
  |  First Published: December 2013

Many lure and fly fishers spend a lot of time agonising over the colour of their offerings. But how much difference does colour actually make?

In the last two instalments of this column I’ve looked in some detail at how fish might see their world. We learnt that most fish, and especially the shallow water and inshore predators we typically chase, have very good eyesight. Also, we know that the majority of these fish can also perceive colour, although the part of the colour spectrum visible to them may be a little different to the one we see (for example, some fish can detect reflected ultraviolet light, which is invisible to us).

However, there’s something else we need to factor into this equation, and that’s the way in which water (even very clear water) progressively absorbs light of different wavelengths. This means that colours effectively ‘vanish’ one after another as ‘white’ sunlight travels through the water column. With increasing depth (and also with increasing horizontal distance through the water), the colour in sunlight is absorbed, and the amount of visible light also diminishes. Because absorption is greater for longer wavelengths (the red end of the spectrum) than it is for shorter wavelengths (the blue end of the spectrum), perceived colours are rapidly altered with increasing depth (or distance).

The exact rate at which this loss of colour occurs varies considerably depending on the intensity of the sunlight (directly overhead or low on the horizon, cloudy or sunny conditions and so on), the clarity and colour of the water itself, and the presence of any suspended matter, such as weed or plankton in that water. Even in very clear ocean currents far from shore, less than 25% of available sunlight hitting the water’s surface will penetrate much beyond 10m. By the time we reach a depth of 100m or so, the remaining light may be as little as 0.5% of that available on the surface. In other words, it’s pretty gloomy down there!

As mentioned, red is the first colour visible to our eyes to disappear, and this colour is typically gone within 5-6m (much less in dirty water). Orange disappears next, then yellow, followed by green and purple. Blues (both the tones of blue visible to our human eyes and also the shorter, ultra-violet wavelength many fish can see) penetrate deepest of all.

This scientific phenomenon has a profound impact on the way things look to us (and presumably also to fish) underwater. White objects will appear bluish underwater, with the darkness of that blue increasing with depth. Red objects will begin to look dark or even black within a few metres of the surface. Down at 15-20m, even in clear water, the world appears to be composed entirely of shades of grey, blue and black.

It’s worth stressing that this loss or alteration of visible colours occurs in both the vertical and the horizontal plane. So, 15m of vertical depth has roughly the same impact on light waves and colour reflection as 15m of horizontal separation between object and observer. In other words, a red lure may look black when viewed at a depth of 15m, but it’s also likely to look black, or at the least very dark grey, when viewed from the side at a distance of 15m, even if it’s up in the surface layer.

At face value, this phenomena of colour loss at depth would appear to make a mockery of the importance of colour in lures anywhere beyond shallow, ultra-clear flats fishing. However, most experienced anglers know that lure colour can sometimes make a difference, even in deepwater jigging. Maybe we’ll never understand exactly why, although it’s certainly an interesting subject to ponder!

While I accept that colour can be a critical component in lure and fly choice on its day, I generally rate colour well down the list of key selection criteria, below things like size, shape, action and running depth. In my opinion, far too many fishers get completely hung up on the colour question, often at the expense of other factors that are at least as important to their chances of success. By all means consider colour, but don’t let it dominate your thinking!

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