How to style DGN?

If you need to know what they are... a seed file is an existing DGN file that is used like a template. All MicroStation output is created using one of these seed files as a template. Always. The cell file stores cell definitions. Cells are like map symbols for MicroStation. There are lots of different types of cell and it's worth being aware of what different types there are and what you want to use.

So you always need a seed file, but don't always need a cell file (also known as a cell library) unless you are planning to use cells. There are various seed files provided within FME - for 2D or 3D, and for units of either feet or metres. There is also a standard cell library I think, though it doesn't have many cells in.

You set the seed file in a writer parameter (see in the Navigator window). You can also set the cell library there I think, but usually you'd set it in the DGNStyler where you use it. The DGNStyler will apply the cell you specify to any incoming point features.

The DGNStyler also lets you apply line colors and area fill for different geometry types. You can set a different color based on an attribute by selecting the drop-down box to the right of a parameter, and choosing the option Attribute Value.

Anyway, that's the basics. I hope this helps.