There typically is redness and "graunularity" or a increased reflectiion of light seen on the surface indicating inflammation under the surface. The above picture is of the lower portion of the stomach, known as the antrum. It is the area of the stomach that is most prone to infection from Helicobacter pylori, the bacteria that predisposes to stomach, ulcers and stomach irritation from aspirin or other medications. The pylorus is the opening leading from the stomach to the first part of the small intestine. It can be involved with ulcers, resulting in narrowing or stenosis. Congenital narrowing can happen in infants known as pyloric stenosis.

Biopsy of the antrum of the stomach is routine to look for the H. pylori bacteria that can cause ulcers or predispose to stomach cancer. If present in context of symptoms, ulcers or a family history of stomach cancer or ulcers, H. pylori is treated with combination of antibiotics and acid blockers. 

 

Chemical irritation of the stomach, also known as reactive gastropathy or gastritis, is common. Aspirin and aspirin like arthritis or anti-inflammation or pain relieving medications known as non-steroidal anti-inflammatories (NSAIDS) commonly cause reactive gastropathy or chemical gastritis. These include in addition to aspirin products, common arthritis/pain relieving medications available over the counter (OTC) such as ibuprofen, advil, aleve, naproxen, and motrin as well as prescriptions NDAIDs such as celebrex, indocin/indomethacin and naprosyn. Bile can also cause reactive or chemical gastritis (see question and answer below)

Bile is also a common cause of reactive or chemical gastropathy. Biopsies of the stomach will show what is called "reactive gastropathy/gastritis".
Bile is not an acid but is alkaline. So acid blockers (zantac, tagamet, pepcid, prilosec, nexium etc) don't relieve the pain. It is made by the liver and secreted from the bile ducts and gallbladder into first part of the small intestine known as the duodenum. Bile aids digestion, as a detergent. It is normally not in the stomach but can regurgitate backwards from the duodenum through the pylorus into the stomach. When bile regurgitates back into the stomach it is very irritating to stomach and causes intense redness of the lining (seen here in photo along with ...yellow bile color) as well as symptoms of nausea and abdominal pain. The stomach usually appears reddened (erythema) and granular and bile is usually seen (as greenish fluid) in the stomach. Causes of bile backing up in the stomach include poor stomach motility/movement or emptying (gastroparesis) that is a common complication of diabetes; excess bile reaching the duodenum (over secretion especially after galllbladder surgery resulting in lack of storage space for bile between meals), and idiopathic or unknown reasons. Diagnosis is confirmed by upper endoscopy (EGD) and biopsy. It is treated by coating the stomach to protect it from the bile irritation (e.g. with gaviscon or sucralafate/carafate) or medications to bind the bile (cholestyramine, colestid e.g.). 

This photograph is of a biopsy of normal stomach. Note the organized glands, some of which have clear "goblet" like structures that secrete mucus that helps protect the stomach against injury including our own acid. There is a mucus layer that can be seen faintly over the surface lining. The bacteria Helicobacter pylori likes to burrow under this mucus layer and triggers increase inflammation type cells in the stomach lining. The bacteria can trigger changes that make the stomach vulnerable to ulceration was well increase the risk of stomach cancer and a type of lymphoma of called MALT lymphoma. That lymphoma, a form of cancer, can be cured frequently with just antibiotics to rid the stomach of H. pylori bacterial infection.

The stomach has slightly salmon pink to orange-red color on surface. It is common for some redness to be present since it does contain acid and other digestive juices. This photo is of the lower portion of the stomach called the antrum. It is just before food leaves the stomach through an opening called the pylorus to enter the first segment of the small intestine known as the duodenum. Most ulcers occur in the antrum of the stomach, within in the pylorus or in the first portion of the duodenum known as the duodenal bulb. The bacteria Helicobacter pylori likes to infect the antrum of the stomach, where it can burrow underneath the protective mucus layer of the stomach and cause inflammation that predisposes to ulceration, cancer and lymhoma of the stomach.