In engravings and line drawings, it is hatched using a field of evenly spaced dots.
It is very frequently depicted as yellow, though gold leaf was used in many illuminated manuscripts and more extravagant rolls of arms.
[1] The use of "gold" for "or" (and "silver" for "argent") was a short-lived fashion amongst certain heraldic writers in the mid-20th century who attempted to "demystify" and popularise the subject of heraldry.
"Or" is sometimes spelled with a capital letter (e.g. "Gules, a fess Or") so as not to confuse it with the conjunction "or".
[2] However, this incorrect heraldic usage is not met with in standard reference works such as Bernard Burke's General Armory, 1884 and Debrett's Peerage.