Hi flashman

Assuming that you are carrying a backpack you could always use a D12 Reversible Backpack Cover

As you have stated clothing is so important in a survival situation and choosing the correct clothing is essential for the environment most find themselves in. I do prefer muted colours and sometimes will wear camo if I don't want to be seen (mostly British DPM simply because it suits the environment in Northern Europe and has not been bettered). Walking through the forest wearing garish clothes may be useful if you tend to get lost, but being ex - Foreign Legion, I doubt this will happen to you. The downside to wearing garish clothing is that all the wildlife can see you traipsing down the trail also (useful for bear country though). If you wish to get a real feel for the wildlife inhabiting the forest then OG or camo is required together with moving silently.

As for weather protection, I have generally moved away from synthetics except for 2 different fabric technologies, that being Goretex and Gore Windstopper. Polypropylene under garments have been replaced with merino wool, polyester fleeces replaced with merino wool and the windproof layer being cotton Ventile. Synthetics are smelly and have to potential to turn you into a human candle. The Gore materials are used mostly when encountering much higher altitudes above the tree line. There is really no substitute for Goretex socks, gloves or head wear in very cold and wet conditions though. If it is really chucking it down at low level I will wear a S95 goretex liner in conjunction the Ventile jacket and some German Army Goretex trousers (the ones with the braces).
For sub zero temperatures at camp I will either wear an Alpkit Down Jacket or a Snugpak Sleeka Reversible Jacket and trousers (Similar technology to the Snugpak Softie Special Forces sleeping bags).