Coffee table
Reminds me of Kramer's "coffee table" book.
Maybe you should also put a coffee book under or on top of the glass?
The dark roasted, oily coffee beans (black) will turn dull and matte surface as the oils break down and re-absorb into the beans. The lighter roasted (brown) coffee will age well. Green coffee fades (higher grown, harder beans fade slower than low-grown seeds) = first losing green vibrancy, then becoming more beige/yellow. Monsooned green coffee is already faded to about the limit. Parchment coffee lasts pretty well = only fades from yellow/beige to paler white-ish/beige. Natural process (dry prep.) coffees age well = whether seeds, complete cherry or broken husks.
Air, direct sunlight and hot lights will accelerate the aging, while flourescent lighting has little impact.
I have not tried this, but the epoxy stuff (extra-thick polyurethane types of woodfinish) that was popular table coating material might slow the aging process (except for sunlight fading).
A friendly roaster might offer you a low cost for stale "waste" inventory, which might not fade much more.
Good luck with your project ~> post a photo of your finished table!