I'm planning to make my own sandbags but i'm wondering what color to use for painting them. I tried painting sandbags before but they don't look like sandbags. Any tips? I couldn't find anything on this site but if anyone knows were to look, let me know!

Baldy,
sandbags are relatively easy- use an earth brown shade, then mix in some dark brown and black in some irregular patterns. Remember, sandbags usually get damp, dirty, split open, etc. so there isn't a hard fast rule. just use your imagination, and you don't want them to look exactly alike! Hope this helps. Oh, and welcome to the site!!

Welcome Baldy
I myself like to use shades of khaki for sand bags. This is for a desert scene mind you. Darker shades of brown in a European environment. I guess it all depends on what their made of and whats in them.
I hope this helps!

some of the sand-bags I've seen can have a light green hue about them maybe to do with the natural materials used a light dry brush on a couple would look good to break them up a little

The answer very much depends on where and when you want to depict. You can have tan, brown, or green coloured bags that then have a dusting of your earth/sand tones.