In 1972 and 1973 (August through the winter to March), the United States Army Mobility Equipment Research and Development Center (USAMERDC) along with the Mobile Army Sensor Systems Test, Evaluation, and Review project (MASSTER) developed new camouflage guidelines using a variety of drab or earthy colors, replacing the previously used overall FS 24087 semigloss olive drab base color of vehicles. The schemes, suitable for eight different environments, began to be implemented in 1973, being tested on vehicles at Fort Hood. Units overseas (such as the US 7th Army in Germany) at the time that did not have access to these exact paints came up with expedient camouflage schemes until they could receive the proper paints, and sometimes used their own schemes alongside the MERDC ones. On August 28, 1975, Technical Manual 5-200 Camouflage Pattern Painting was released.

The standard camouflage colors listed in TM 5-200;

As a part of this scheme, the white stars and registration numbers, previously readily visible on vehicles, were to be repainted in black or more commonly, left off entirely. A variety of four-color combinations were tested. Colors 1 and 2 each cover about 45 percent of the vehicle, while colors 3 and 4 each cover about 5 percent. Here are illustrations of what the various schemes looked like, overlaid on a simple M109 Paladin vehicle drawing (here and here are some more "realistic" paintings of the schemes, on M1 Abrams) Sometimes, the Sand color was left off of the winter verdant scheme, making it easy to confuse with the three-color NATO camouflage adopted in the mid-1980s.

1: Verdant means generally green--in summer due to trees, shrubs, and grass; in winter due to evergreens.

2: This color combination is for use only in areas that occasionally have snow which does not completely cover the terrain, thus leaving trees or patches of soil bare.

3: This 5% color should be the camouflage color that matches most clearly the color of the soil in the local area. A typical color for such use is sand, but earth red, earth yellow, or one of the others may be closer to the predominant color, and in that case, should be used.

Sources:

Report 2090 Camouflage Pattern Painting Report of USAMERDC's Camouflage Support Team to MASSTER, by Adolph H. Humphreys and Sharon V. Jarvis (February 1974)

MERDC camouflage

MERDC camouflage illustrations

Standard Catalog of U.S. Military Vehicles, 2nd Edition, by David Doyle

M551 Sheridan: US Airmobile Tanks 1941-2001, by Steven J. Zaloga

M1 Abrams Main Battle Tank 1982-92, by Steven J. Zaloga and Peter Sarson

Heres what i know about that white star in the circle!

It began as an aerial marking for all allied forces around 1943 after previous designs received complaints from airmen trying to decipher them from their planes. This was particularly true in North Africa where allied airmen had a hard time distinguishing between not only the various tanks on the battlefield but also their symbols. The German cross was too close to a plain star! Basically they were a way for all allied air support from various nations to quickly identify friendly forces on the ground so it had to be very clear who was on whose side. By the time of the D-Day Landings at Normandy, it was the universal symbol in use for that purpose

It was phased out officially due to changing army camouflage and vehicle marking protocols. This is most likely due to two factors: One is more obvious... As WWII ended, the "allies" no longer existed as a unified army and therefore all symbols of that uniformed, multinational force would become obsolete over time. Remember this wasnt just a symbol used by the US. The UK, Canada, Australia, Free French, and other allied forces all would have painted that white star in a circle on their vehicles. Continuing on with it after the war could be potentially confusing. The other reason is less 'official' so take it with a grain of salt. During the Vietnam war it became rather apparent that painting a large white star on your tanks and trucks was a great way to get them noticed and shot at in the jungles and at night. Considering the nature of air support changed, communications got better, and the enemy was largely un-mechanized... the need for a clear visual marker on top of tanks and trucks to prevent friendly fire and aid in recon just wasn't there anymore. And so the star became nothing but a liability on the battlefield.

I hope I answered your question! I had been curious myself about the star-in-circle when i saw it on photos of brit tanks.

"American Military Camouflage and Markings 1939-1945" by Terrence Wise (Almark Publications 1973).

"There are six different types of national identification symbols to be seen in photographs of US army vehicles during World War Two, five of which are variant of the well-known white star, used on all Allied vehicles from the Normandy landings of 1944 onwards. It would appear therefor that the white star was the direct descendant of the earliest versions, all of which were but transient stages in the development of a national identification insignia..... The Star and Circle: A plain white star,surrounded by a continuous or broken white circle, this came into common usage towards the end of 1943 and continued in service throughout the remainder of the war. It was specifically designed as an aerial recognition symbol,but was painted indiscriminately on most parts of all vehicles in North West Europe and Italy, although it does not seem to have been deployed much in the Pacific theatre of the war. This marking was used by all the Allied forces at this time."

"All American Wonder, vol. 1" by Ray Cowerdy (Victory 2nd edition 2001)

"Armor Camouflage & Markings North Africa 1940-1943" by George Bradford (Bradford 1971)

"US Armour Camouflage and Markings 1917-45" by Steven Zalgoga (Osprey 1984)

US Army Regulations AR-850-5 (1942, 1943, 1944)

The original vehicle insignia was a white star on a blue background with a red dot in the middle, just like the early aircraft insignia. It was later changed to omit the red dot. This symbol was dropped in 1942, but a few halftracks still had it on the hood during Operation TORCH. The white star (with bars when on tank turrets) was adopted in its place. Armored Force vehicles (mostly those in tank divisions) used a yellow star from January to August 1942. The star surrounded by a white circle was commonly used in late 1943 because it was thought the star on a dark background might be confused with the German balkenkreuz.

The white star was phased out starting in 1975, when the Mobility Equipment Research and Development Center (MERDC) 4-color camouflage scheme was adopted. The major reason for the new emphasis on camouflage was the increasing range of tank and anti-tank engagements. The white emblem could no longer be seen well at likely engagement ranges, so no longer served well for identification, and camouflage worked better at the longer ranges. The white star was replaced with the same-sized star in matte black, as shown here. The MERCD's 1974 report states that "Eliminating, or painting in lusterless black, the star and administrative marking on a vehicle is the most important factor in reducing its visibility". Eventually the larger black star was replaced with a small black star, usually front center and rear center of the hull/body.

"Camouflage Patern Painting Report of USAMERDC's Camouflage Support Team to MASSTER", February 1974.

"Long Range Target Recognition and Identification of Camouflaged Armored Vehicles", May 1979.

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