The two main devices (symbols) in the Margaret blazon are the eagle and fesse. The two main tinctures (colors) are azure and argent.
Azure is the heraldic colour blue, usually quite a deep, dark shade of the colour (there is a lighter blue that sometimes occurs, known as celestial azure). If colour printing is not available then it can be represented by closely spaced horizontal lines in a scheme known as “hatching” 1Boutell’s Heraldry, J.P. Brooke-Little, Warne, (revised Edition) London 1970, P 26. The word is thought to originate from the Arabic lazura and it represents the colour of the eastern sky. It is also said to be the colour associated by the Catholic Church with the Virgin Mary and hence of particular significance 2The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P150.
Argent is the heraldic metal Silver and is usually shown as very pure white. It is also known more poetically as pearl, moon (or luna) 3Understanding Signs & Symbols – Heraldry, S. Oliver & G. Croton, Quantum, London, 2013, P53. In a sketch or drawing it is represented by plain, unmarked paper 4A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1847, P11.
Where the lion is undisputed king of the animals, the eagle undoubtedly plays the same role in the realm of the birds, its use in this form dating back to at least the Roman period 5A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Eagle. They tend to be illustrated in quite some detail, especially in continental European arms, and have almost as wide variety of postures and accessories as the lion, well illustrated in the reference 6A Complete Guide to Heraldry, A.C. Fox-Davies, Bonanza (re-print of 1909 Edition), New York, 1978, P235-238 as well as being just the eagle’s head or eagle’s leg. The symbology of the eagle is deep and complex, Wade devotes several pages to the subject 7The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P72-74, but suffice it say that it has long been associated with Empire and those held in high honour – any armiger would be pleased to have any form of Eagle upon their arms!
The fesse (also found as fess) is one of the major ordinaries to found in heraldry, being a bold, broad, horizontal band across the centre of the shield. It may originally have arisen from the planks of which a wooden shield can be constructed, the centremost plank being painted a different colour 8A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Fesse. It is instantly recognisable as a symbol, for example the arms of COLEVILLE granted during the reign of Hery III are simply or, a fesse gules. With this clear association with the construction of the shield itself, Wade believes that the fesse can be taken to be associated with the military, as a “girdle of honour”.