If you're concerned about monument feeling too oppresive, you could always go a couple of shades lighter, say Basalt or Windspray (if you're looking at colorbond colours), which will still give you a modern feel and enhance planting in front. Or you could allow the timber to weather to a natural grey. If there's going to be plants covering it up eventually it will save time, money and further maintenance with repainting. Just be aware with a narrow bed, you're going to be limited as to what you can put in there. Consider ongoing maintenance - (ie how do you trim a hedge, are leaves and flowers going to be an issue) and I would advise putting in a raised edge to minimise water pooling in the garden bed and drowning the plants. Additional drainage will also help to remove any excess water from the bed from splash. It may be worth getting professional in to have a look and offer some suggestions. Many landscape designers offer consultation services. They will also be able to help with colour advice, taking into consideration the house and aspect.

PLEASE do not laugh at my sketch skills... it is the first time using it and am just trying to picture colours together :) so here is a pic of my house. On the left i have added the white fence and on the right it is the surfmist. I thought to go white slats on top of surfmist and a full white slat gate on the left because the white will match the pure white wall and aluminium and the surfmist part of the fence will match the garage door, that way it all ties in. What do you think?

Start again, but this time in a charcoal colour. Charcoal on the fence is always a fantastic backdrop for the greenery of plants.

Personally, I think it's absolutely fine for the fence color to change as you enter the gate into the back garden. Since you can't see both the front and back fences simultaneously, it shouldn't be too noticeable. Plus, it's your space, so go for what makes you happy! If you're looking to enhance your outdoor area even more, you might want to consider adding some https://www.scottsofthrapston.co.uk/ —they can really elevate the vibe of your backyard.