The problem with geographical color palettes will likely be that the inspiration comes from a very specialized topic.
You're not looking for a random allocation of color, so you need a reason for associating a color with a region - one that users might identify with.
Example inspiration might come from:
- Geology (earth/rock colors associated with a region)
- Elevation (green-brown terrain map)
- Vegetation (lush green, arid brown, desert yellow, salty white)
- Temperature (red hot, ice blue)
However, these are usually linear scales for mapping purposes. You also need a palette that doesn't vary, so vegetation or temperature might be out.
Alternative inspiration might come from:
- State University brand colors
- Football/baseball team colors
- US State colors
But whatever you pick from these types of inspiration, it's likely to be too subtle for most people because the reasons for your color selections will indeed be your reasons, and won't be directly associated in the user's mind unless you had a legend telling the user about the color palette.
In any case, brand colors are the color of the brand, and if you used (similar) brand colors, you look like the brand and lose individuality.
You need to have a more tangible reason for choosing colors. Being 'regional' isn't enough for most scenarios. John Deere's grassy green and wheat/crop yellow is a great combination, but it's not because of a region. It's a direct association with the immediate environment - it works anywhere their equipment might be used, and so is entirely non regional!
In the digital and distributed age, it seems a strange choice to try and create associations that are too localized if you are trying to appeal to a wider audience. Most people won't get the connection.
Color is the primary communication tool and the best advice is to use a color palette that works well, is consistent and is accessible. The appeal will come from the visual effect, the tone and neutrality, and the composition, not because the colors are regional to you.
Imagine explaining your palette reasons to an interviewer. What would the interviewer care about?
Greens and browns that might work agriculturally in the mid west for example, might not be great for your resume, and might be completely lost when a prospective employer prints it out in black and white, or shows it to a color-blind colleague.