Use only the manufacturer's recommend products on your leather sofa, unless you are prepared to have a damaged hide on you new piece. When incompatible chemicals are used on furniture grade leather, it typically causes a stripping of the topcoat and the hide is ruined. What's worse, this stripping does not show up right away and occurs several months after application of the product. By that time the leather is ruined. I would check with the maker of the sofa before I would use any product on the piece.

They spray on the color. It is very possible to change colors depending on what you are changing to and from. Cost would depend on the style of the sofa.

There are so many jeans that seem to be saturated with dye, especially the indigo blue ones. I can understand your concern. I do have a pair of light colored leather club chairs, which are heavily used. I clean them with a good leather cleaner a couple times a year, and they still look great. I haven't experienced the dye issue, but maybe anyone with the oversaturated jeans haven't sat in those chairs. My3dogs, what a great resource! I bookmarked it for future reference.

It looks like the Cleo bed from vanguard. I'm not sure about the bench. https://vanguardfurniture.com/pages/products/sku/W521K-HF