It's better to just make more runs with the storage you have. Eventually you will get lucky and a white or black dye will drop. This is what you are looking for. Sell it to other players, or save it until you can get to the dye trader after the Searing. To make your farming easier, it is a good idea to get all the bags you can. In Pre-Searing Ascalon, this means you get a belt pouch from a collector. You might also get some charr bags, but these run for 500 guild wars gold or so and in Pre this is a lot of gold. 

It can be hard at first to get any guild wars gold in this game, but if you are patient and like to hunt, you will not have to beg for the 50 guild wars gold to open your storage locker like so many people in this game. Monsters might drop one or two gold coins, but mostly they dropped useless items. That's where the merchant comes into play. Merchants will buy all your drops. Making gold is now only a question of killing monsters and selling the loot.Get the best weapon you can and if you need materials for a weapon, use salvage kits to break down drops. I made enough this way to afford the best weapon, as well as start a guild. 

You can't see what the trader will pay unless you have the rune or insignia in your inventory, but you can get an idea of its value by seeing what he's selling them at. The non-valuable ones all sell for 100 g, and the trader will buy those at the merchant price of 25 guild wars gold. The merchant also values runes and insignia at a fixed price, being 25g. Once again, certain runes and insignia command much higher prices at the trader, depending on in-game demand. You get runes and insignia by salvaging them off blue, purple and guild wars gold armour, so it's worth checking the trader price first to see whether it's worth salvaging.