The conventions described on this page are often arbitrary. In many cases other options would work just as well. If there are good reasons for preferring one way of describing a stamp's features we should still be prepared to discuss possible changes.
The standard for describing perforation is the number of holes (or the "teeth" or perfs of an individual stamp) in a 2-centimeter span. If a stamp has more than one perforation size, the standard practice is to list the gauge of the horizontal edge first and then the vertical. For example, if a stamp is perforated with gauge 11 on the top and bottom but 10 1/2 on the left and right edges, it will be designated by 11 X 10 1/2.
If, however, the stamp is only perforated on two sides (top and bottom or left and right edges), the standard designation will include the size followed by a 'V' or 'H' depending on whether the vertical or horizontal edges are perforated.
Sadly, printed catalogues do not follow any standards that would put them in conformity with each other. Often these catalogues are not even internally consistent. The good news is that in most cases it is not the most important feature to be used for identifying a stamp. While we should be aware of the general coloring of a stamp, there is no objective standard that could be broadly applied, except to say that English colour names should be used for this English Wikibook. Colours in certain other key languages may be added on an optional basis.
Stamps in two or more coloursEdit
When describing such situations Scott catalogues name the outer colour first; Gibbons catalogues name the inner colour first. I would suggest naming the inner colour first followed by the word "in".
Please read wikipedia's stamp paper article for in depth description of paper types.