Can You Hire an Interior Decorator Just to Help You Pick Colors/finshes?

I'm an interior designer (was before I was a SAHM anyways). Its called consultation. I don't know where you would find one. You need to find an independent self -employed designer or small residential firm that takes on small projects.
But the answer is yes, many designers will work with you while you do your own leg work, research, selections, and documentation.
They can tell you if everything is working well together, direct you to appropriate materials, and perhaps pull a few paint colors and fabrics for you from their vast resources. Maybe they help you develop your concept, color story, or furniture plans, while you do the rest.
I think its a great way to use a designer if you are trying to get the best bang for your buck. Just know that while a designer in that role can help someone stay on a good path and prevent them from making costly mistakes, you're not likely to end up with something that looks like it belongs in a magazine.
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to add, I have also pulled finishes for people (paint, granite, wood finishes, flooring), To give them a cohesive base, handed them the samples (or written up simple specifications (manufacture/ style/color) and let them take it from there.
While many designers offer full service design, you don't have to use them for full service design (concept development, drawings, budgeting, sourcing, specifications, purchasing, project management). Again using a designer for for ideas and direction is called consultation.

I am sure you could also look on AngiesList.com to find one as well.

Yes, I did this, hired an interior designer to help me select colors for my house as it was being built. She also walked through and gave me furniture ideas, just general concepts that I used when shopping to furnish our new house.

Some furniture stores provide free consultations in your home, if you buy furniture from them. You'll want to find someone whose style meshes with yours. You can google and check out a few local designer's websites to start. Then call to see if they'd be willing to work with you by the hour.

Sure. You can negotiate anything. You could go to sample houses in your area that you like and ask the who then decorator is to find one.

I am in your exact position.

I have interviewed 5 interior designers. They all charge by the hour and help pick out all of these things. There hourly rate vary from $75 to $115.

I just chose my interior designer yesterday.

If you would like the name of the people I have interviewed, please message me and I will give you their contact information.

Many furniture stores offer that service. Check websites. Or check online for interior decorators in your area.

Yes, call around. I did the exact same thing (for paint colors only) and it was totally worth it!