Eugene Volokh asks why so few countries use brown or orange on their flags and wonders if they are just "cross culturally ugly or non-patriotism-inducing colors. Hmm, I don't know. I do know the good folks of Cleveland seem to enjoy them just fine. I don't think any one ever accussed Cleveland Brown fans of not being fierce defenders of their team. In fact, from what I understand, the colors are actually an integral part of that bond.
For what its worth, according to this page 4.69% of nations (or 9) have flags with brown in them and 4.69% of nations (or 9) also have flags with orange in them. While certainly not the most popular colors, they are nonetheless fairly well represented, with 18 countries total containing at least one of the colors.
Countries with Orange include India, Ireland and Armenia ... all nations with very patriotic citizens.
While Andorra sports brown on its flag both Mexico and Zambia also include the color and make up for poor Andorra's lack of overt patriotism (poor Andorra is the country my grade school geography teacher insisted did not exist and was simply a flaw on the map - when I corrected him in front of the class he was less than pleased with me).
So you see, I just don't believe the myths about brown and orange. They are used and they are loved colors.