I created a shape file a while ago with several (20+ polygons) in it. I was wondering if there is a way to symbolize these polygons with unique symbols.
Basically all I actually want to do is color them differently from each other, and I don't think I can do this when they are all in one file.
You can color different polygons in one shapefile differently - you don't need to put them in separate shapefiles. You do it through the Layer Properties and the Symbology Tab.
Once you are on the Symbology tab, you have a number of choices of how to symbolize your data. Which option is best depends on the type of data you are working with the information you have in your attribute table.
If there is a field in your attribute table that has a unique identifier for each polygon (which it sounds like from your question), and you would simply like each polygon to be a different color, you can choose Categories and then choose Unique Values.
Under Value Field, choose the field that contains the unique values and then click Add All Values at the bottom. Once you have this set, you can change the color ramp or modify the colors for individual values.
In this example, I symbolized a shapefile of Pennsylvania so that each county is a different color. This is what my Layer Properties window looks like:
And this is what my results look like on my map:
If you're using ArcGIS Desktop 10.0 software as the tag on your question suggests, all you would have to do is bring that shapefile into ArcMap. Then, right click on the resulting layer for that shapefile and select "Properties..." from the bottom of the context menu. Then go to the "Symbology" tab in the Layer Properties menu that should open up. On that tab select the "Categories" option and the "Unique Values" suboption. Then all you should have to do is select a field to use as the "Value Field". What this means is that each unique value in that field would be able to be drawn with a different color. So, if you had lets say 20 polygons and you had a field called region with the 20 polygons split between 3 different regions. You could symbolize on the region field and you would have 3 different colors.
However, if you are trying to draw every individual feature/polygon as a separate color, then you will want to make sure there is a field with a unique value for each feature (other than the ObjectID field). You could do this, if necessary, by adding a new field with field type LONG to the shapefile's attribute table and calculating that field to be the same as the ObjectID for each feature. Then you can go back to the symbology properties use that new field as the unique value field on which to symbolize. With that field selected, click add all values and, if necessary, change the color ramp to the desired color scheme. You can then, if needed, go back and change the colors for individual features by double clicking on their symbol.
