How brown does it look? If it looks closer to motor oil then trans fluid, most people will suggest not to touch it.
I wouldn't do a flush, but if you do anything I'd drop the pan, change the filter and possibly the gasket (gasket is usually included with filter.)
Changing the gasket is not required if you have the original re-usuable gasket.....You can usually tell by the appearance of 2 lines that run along the gasket. Here is an example.
You must replace the gasket if it is not the original gasket OR if it is leaking.
The site where I found that image also has a write-up for dropping the pan and changing the filter. That link is located HERE.
