Overheads of Bitmap over DrawRect

I can't say this 100%, but I imagine using DrawRect with solid colors has less overhead than loading 100 bitmaps. I think most developers would choose DrawRect with solid colors instead of bitmaps. Is there a reason you would need to use bitmaps?

Thanks for the reply.
The reason for querying bitmaps is because I need either an Ascii arrow or draw an arrow with Drawline, on some rectangles and I wondered if it was better to have a bitmap with the arrow.
I accept your opinion on overhead and will not follow the bitmap path.