If you’re simply doing touch-up work , you don’t need to match the paint that you used previously - make it instead as a visible repair to the concrete. You can save money and time using the Floquil Concrete that you have, without need to alter it at all. This will also serve to give a sense of age to that piece.
Wayne
Great idea. Thank you.
Gray mixed with tan, in amounts depending upon how gray or tan you want the concrete to look.
Add black or white to darken or lighten.
99 cent tubes from Walmart will do. And you can always use those 4 colors in just about any painting or weathering job.
Using Rich’s recipe as a guide, and the paints I had on hand, here’s what I mixed:
FolkArt Wicker White – 10 parts
Anita’s Shamrock Green – 2 parts
FolkArt Dove Gray – 2 parts
Ceramcoat AC Flesh – 2 parts
Anita’s Dark Red – 1 part
Anita’s Earth Brown – 1 part
This is what I came up with:
Which is pretty close to Vallejo Cement and Concrete
I’m pretty satisfied with the results. I can mix a batch in my 17mm bottles.
Terry
Excellent results, Terry.
When I posted that formula four years ago, Pollyscale paints were still generally available. So colors such as D&RGW Building Cream were part of my formula. But your mix demonstrates that most any brand will work.
When I first developed that posted formula, I used Tamiya Acrylic White, Green, Red and Brown along with Pollyscale D&RGW Building Cream and Reefer Gray. The key is to use acrylic flat types of paint. But, any brand of acrylic flat white, green, gray, cream (flesh) red and brown will work.
For tiny amounts of mix, just use a toothpick to dip into the paint bottle and let drops of paint flow into the mix.
Good luck.
Rich
Off the shelf, Model Master Aged Concrete is a good match. You can find it on eBay as well as hobby shops.
Rich
That’s ok and I understand your point about buying too many paints from different companies.
Good luck for your project. I would like to see some photos 
Thanks Rich, and thanks for sharing your formula. Also, it would be easy to lighten or darken the mixture by slightly altering the “parts”
Terry
The colour of concrete, new or aged, depends on where you live. The concrete model paint I’ve seen has a cream or pale yellow tint. Concrete where I live (Ontario, Canada) doesn’t. Instead it’s a light grey. I think the difference is the gravel used - crushed sandstone in at least part of the USA, crushed limestone in Ontario.
To complicate things more, the city I live in coats street curbs with a hardener. They look like they’ve been painted white, but after a few years fade to grey.
Actually, it depends on where you are modeling.
Rich