The main device (symbol) in the Sas blazon is the cross. The two main tinctures (colors) are gules and argent.
Red in heraldry is given the name Gules, sometimes said to be the “martyr’s colour”1The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P36. The colour is also associated with Mars, the red planet, and the zodiacal sign Aries 2Understanding Signs & Symbols – Heraldry, S. Oliver & G. Croton, Quantum, London, 2013, P53. Later heralds of a more poetical nature would sometimes refer to the colour as ruby, after the precious stone.3A Complete Guide to Heraldry, A.C. Fox-Davies, Bonanza (re-print of 1909 Edition), New York, 1978, P77.
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) 4Understanding Signs & Symbols – Heraldry, S. Oliver & G. Croton, Quantum, London, 2013, P53. In a sketch or drawing it is represented by plain, unmarked paper 5A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1847, P11.
No other symbol appearing in heraldry is subject to as much variation as the cross 6Boutell’s Heraldry, J.P. Brooke-Little, Warne, (revised Edition) London 1970, P 47. Mediaeval Europe was a deeply religious and Christian and many of the nobility wanted to show their devotion by adopting the symbol of the cross as part of the arms. In its basic form, the cross is created from two broad bands of colour at right angles covering the whole extent of the shield. It has been subject to all manner of embellishment, and the interested reader is referred to the references, especially Parker’s Heraldic dictionary for many examples of these. 7A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Cross 8A Complete Guide to Heraldry, A.C. Fox-Davies, Bonanza (re-print of 1909 Edition), New York, 1978, P106 9A Treatise on Heraldry, J. Woodward, W & A.K Johnston, Edinburgh & London, 1896, P160-173 Suffice it to say that any armiger would be proud to have such an important device as part of their arms.