Hi there,
Had a look at the app you require, It would be hard to code color changes unless you can provide SVG's of all rooms. Otherwise I would code for you as follows:
In backend
1) you upload the image of room type
2) you add products
2.1) product preferences, fabric (colors/patterns) and other settings like price or whatever you require, you would have to upload images for each room type+fabric combination, and this would be the most problematic part for you as you would need lots of images, especially if we add in rail color to our combinations, let me know if you have a better idea how we could handle this
3) associate products with room types, this would make this product available on the UI side as on gemini-blinds, when user selects that room type