Our traditional composite deck boards (NeoTimber Essential and Classic Ranges) shall undergo a level of weathering (lightening-up) within the opening 3-6 months of installation. This initial weathering process is a result of the boards reacting to UV rays. Once this process has taken place, the rate of change will be nominal.
You may also notice a colour contrast between the skirting/corner trims and your deck boards especially if you are installing the boards wood-grain side up. Once the boards find their weathered colour-tone, the contrast will be more subtle.