This seemingly trivial operation may not be so simple.
Besides assigning a fixed color, AutoCAD entities are often "colored" by their placement in a specific layer. The default color ByLayer then takes over the layer color.
Another possible complication is embedding entities in a block or xref. Such entities can have both ByLayer and ByBlock colors and take over the block color. Their properties can be usually inspected only after opening the xref or block as a separate drawing.
All these problems can be solved with the freeware utility CADstudio GetColor (GetCol). Using GetCol is simple. After you load the VLX file (_AppLoad) and run the command GetCol, it only prompts to select an entity (can be nested in a block/xref) and then it displays the color code (ACI color). It can handle even special combinations of ByLayer and ByBlock colors. For TrueColor hues it displays the nearest ACI color code.
The GetCol utility can be used eg. to prepare a CTB plot style file, or if you want to match the color of an existing entity.
GetCol can be downloaded from www.cadstudio.cz/download