There are amazing shrimp foods on the market. Natural color enhancing ingredients are usually in those formulas.
They need tiny amounts of food 1 time per day if they are in an established tank, set up for several months. In a newer tank I would feed tiny amounts 2x per day.
Someone shared this with me, to think of the fish or shrimps eye as how big a serving size might be. I bet you are over feeding lol!
Over feeding at one time though. They need to be eating through out the day, it is why you see them picking at the rocks, plants and decos, anything in their path, as they are scavengers. An established tank with lots of plants has microscopic food in there and the shrimp are fine eating away on it all through the day. If it doesn't have a healthy build up of bio-film, they could get hungry.
Too much added fish food and water quality can start to decline. So you want to strike a balance of feeding tiny amounts for them so they can grow big and strong.
I use Hikari Shrimp Cuisine, also will add a varied diet of Hikari sinking wafers or algae wafers. The wafers can be broken into small bits to be shared by the shrimp. For 10 shrimp one half 3-4mm Omnivore sinking wafer would be fine in am and pm. Also freeze dried worms, tiny amount, almost any other type of food. The higher quality stuff is worth the money, there is less filler. It lasts a long time since they don't eat that much!
Over feeding can lead to other things you don't want in your tank.
Do you have moss like Java Moss? If you can't find it around you locally I can sell you some reasonably and you can pay shipping. PM me if you are interested. As for plants they love all plants as they eat stuff off of them. The frilly and ones with lots of little edges, like Java Fern Windelov and regular Java Fern too. Echinodorus /Dwarf Swords, Microsword, Anubias. Marimo Moss Balls, Ambulia/Dwarf Ambuila. You can start with low light plants. You can post a separate thread for extra help with lighting plants, in planted tanks.
Also I like Rams Horn Snails for clean up or Nerite if you don't want them reproducing in your tank, also Mystery snails. They are as fun to watch as the shrimp, there are many different colors and patterns too.