How do you realistically render RAL colors on aluminium window frames?

Hi HN Community! This is my first time sharing here, so be gentle :O :D

My wife and I are building a house, and as many enw house owners, we are shocked by the amount of choices we have to make. Not a bad thing per se, but in general, it is quite disheartening when you see it.

One of the choices we have to make are window and door material and color. We are on the fence between going all white uPVC or going for RAL colored aluminium. And here lies the problem – we don't have a way to see how the RAL colors appear on aluminium.

Most, if not all, new builds around use use anthracite (RAL 7016), which we dislike, and we are limited to trying to find examples online with Pinterest and Instagram. Unfortunately, we are quite sure that many images we encounter are mislabeled and showing a different RAL color under a different code.

This has led to me trying to build something to help us visualise the colors. Well, a software engineer tries to solve everything with software eventually. I built something, and it is live here https://protabula.com/en but I am not happy with the way the colors are rendered.

This is my rendering "pipeline", summarised by Claude. I use a base render image and a black and white mask image to isolate the areas that need coloring:

  Applies RAL colors to pre-rendered house scenes using ratio-based tinting in linear RGB:

  1. Load base scene + pixel mask
  2. Convert target color to linear RGB (gamma decode)
  3. Compute adaptation ratio: targetChannel / neutralBaseChannel
  4. For each pixel: tintedChannel = baseChannel × ratio
  5. Blend by mask strength to preserve highlights
  6. Convert back to sRGB (gamma encode)

  Uses adaptive neutral base selection (lighter neutral for light colors, darker for dark).

Do you have experience with this? Does anyone know how to render the colors better? Any suggestions on how to do mapping? Is there some library of materials online that I am not aware of that includes RAL colors? Should I switch to 3d rendering?

Thanks in advance, sorry for the lengthy post, and I hope you have a great New year!

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