what colour lense for dark cloudy backround

what colour lenses do you find best for a dark cloudy background . you know those clouds that look like there is rain coming . i normally use light purple for everything which i find brilliant for blue sky's and green and brown backgrounds but i find i often loose the clay when it transitions from the green backround to the dark clouds . any advice or insight would be greatly appreciated 

Clear

... Or light yellow depending on your particular colour sensitivity

Light yellow. There is a reason these are used for low light conditions when skiing.

clear lenses for all but full sun

gjb said:

clear lenses for all but full sun

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Just to be pedantic (because it's fun), technically all lenses are clear (or you couldn't see through them), so colourless is, in fact, what you suggest. 

I would still argue that various coloured lenses will improve contrast in certain conditions allowing clays to be picked up and followed faster and/or more clearly.

That said, most clay colours are pretty easy to see against a dark cloud background, so in reality, colourless should work as well as anything else.

Personally, I tend to use purple for brighter conditions and yellow for low light conditions.

Possibly this is based on personal eyesight isn't it? Guys I shoot with verge on the majority to using Revision Sawfly military issue glasses with the yellow lens but when I've tried them, for me, personally it's been ridiculously way too bright! Works for them though.

We have to have eyetests every few years for my job and my eyesight always comes back as excellent, 20/20+, so perhaps because of that the acuity with yellow is just to much, even just the clear doesn't assist me, so unless it's stormclouds I go for the shaded ones for me to be able to see the clay without squinting.

Orange clays on a black cloud with sun coming from begind is the perfect combination for clear or ideally for trap no glasses at all.