I have the Overland brown/indigo so I'm looking for something in dark brown or dark blue otherwise I'll just do black because that should work ok.
A company called LLoyd's that makes some funky colors on their Rubbertite mats. No lip on the edges like the heavy duty mats but still look like decent weather protection.
The color sample on the website the brown (Brown #856)
looks pretty dark as well as blue (Blue #854)
but a few other pictures of the colors look weird so not sure. Wish I could see colors in person (edit - I just ordered some samples from an online place).
Rubbertite Custom Fit All Weather Automobile Floor Mats | Lloyd Mats
They also make a clear protector style that lets some of the factory color show through. Not sure if this looks like grandma's sofa plastic protector or not
Protector | Lloyd Mats