Take a look at the real world

I've been doing a lot of Google Map searching (street view) of towns in my home state looking for some general consensus of color schemes on buildings. This seems to be a good approach to discovering what looks good. Not everything looks good painted like it was a Queen Anne mansion on Knob Hill.

That said, you also have to consider the layout is in and who the owner would be. 

What era?

Different eras might have different colors.  1890 might have a darker base color with even darker trim.  1920’s might have a base color with lighter trim, 1930’s-1940’s might have white with a trim color.  After that might have a base color with white trim.

There are also regional differences.  Some southern areas use more pastel colors.  More affluent areas use more colors.  More economically challenged areas would use cheaper more monochromatic paint.

Sometimes all a building kit

Sometimes all a building kit needs is a quick spray of dullcoat to knock the "plasticy" look down.

If the layout is set

in the 19th century, expect to be told "white with weathered grey shingles" a lot. May have a deep colour trim. May also have a white trim on bare, stained wood. Storefront at ground level may be painted a deeper colour overall.

Source: Precision Scale Co.'s Railroad Structures: Buildings of the Old West.

For other time periods, see what paint there was at the time. Today, it could be practically anything.

Yes, I know they're not all wooden, but there aren't that many wooden falsefronts around me...

Color for storefronts

You might want to check this site. they have a color chart for the last century. Its for Photoshop , but it gives a reference  https://graphicriver.net/item/a-century-of-color-retro-swatches/10350329

Pick any

Seriously, you can pick any color. There's stores out there painted in colors that would make Ray Charles flinch.

I believe a lot of them seem to be reflections on interior paint colors at the time; early 1900's tended to have darker exterior paints (dark green, dark blue, etc.) that morphed into the vibrant colors of the 1950's and 1960's, then back towards "medium" colors of today, like grays, browns, seafoam green, and a few others.

If you look at the trend of wallpaper/interior paint at the time, the storefronts seemed to be a reflection on that. Dark wallpaper in the early 1900's, vibrant colors in the 1950's, and more drab neutral colors of today.

Remember that most of these stores are painted by people like you, and the decision is oftentimes just on whim.