Workflow for changing multiple object colors (virtual house painting) in Photoshop?

You’ve gotten some great advice, these might help fill in the gaps:

When I do this, I don’t bother duplicating any of the original image; there isn’t any need to. Like you are doing, I do apply Solid Color Fill layers, but I mask off that layer so that it applies only to the parts of the original image to be recolored.

You asked about the blending modes. That is a menu in the Layers panel, so when the layer you want is selected (in my case, Color Fill 1 for the trim), choose a mode from that menu. For recoloring, the Color mode is usually the one to use, as shown in the demo below.

Any other elements that should use the same color can simply be added to that one mask. In the demo below I subtracted the porch trim from the mask for the Color Fill 1 layer with these steps:

1. With any selection tool, select the trim pieces you want to add. I dragged the Object Selection Tool around the bits I wanted, because it’s one of the smarter selection tools (higher chance of getting it right the first time).

2. With the mask of Color Fill 1 selected, I click the paint bucket icon in the Contextual Task Bar and choose Fill with Foreground Color. As long as the foreground and background colors are the mask defaults (white and black), that command will fill the selection with white, subtracting it from the mask so that the color is now applied to that area too. (The animated GIF color quality in the porch trim shadows is bad because the Adobe forum software re-compresses animated GIF; it looks fine in the original I uploaded.)

3. I look at the mask alone by holding down the Alt key (Windows) or Option key (Mac) while clicking the mask. I Alt/Option-click the mask again to go back to seeing the image with the effect of the mask.

Clicking the paint bucket on the Contextual Task Bar is a rather new shortcut for the traditional method of choosing Edit > Fill and then choosing Foreground Color from the Contents menu, and clicking OK. So this way you can skip the dialog box. Another shortcut for Fill with Foreground Color is to press Alt-Backspace (Windows) or Option-Backspace (macOS).

As you can see, if you want to keep this streamlined, minimal, and easy to manage, all you really need is:

• The original image. 
• One Solid Color fill layer, with mask, set to Color blending mode, for each set of objects for which you want to have separate color control. 

Which means if you only need to show one color for all trim parts, you might not need to add any more layers than one Solid Color fill layer with a mask. Each trim piece would only need to be its own white cutout in that mask. There might not be a need for duplicates and groups, unless you do need finer control over more color variations for different trim pieces.

This is often good enough for a quick and dirty recolor. If it needs to be precise, you can go back later and edit any masks to clean them up.

As an illustration: 

By stacking pixel content with the Adjustment Layers one can do the lower Masks a lot more inexactly in those regions. 

And putting the Groups in a Group allows masking that, too. 

Please post one of the actual images, not a mock-up. 

Using Groups with Layer Masks containing the decontaminated pixel content may offer some advantages.