In my experience, linen dials are usually white/off-white or silvery. I've heard conflicting information about whether the slight variation in color is due to aging, patina, or variation around dial manufacturers.
If you're dealing with established watch dealers, they should be very upfront about it. Usually, linen dials carry a premium when compared to a normal dial. That being said, I have bought a few from random sellers and resellers that didn't know the difference. In those cases, I just looked closely for dial texture (look for the crosshatching). Sometimes I've taken gambles on watches with cloudy/scratched up crystals after forming a hunch that they might be underpriced linen dials or sparkle dials. I've gotten lucky, but If you're not in a gambling mood I would honestly try to stick with what might be more obviously advertised as a linen or textured dial that is accompanied by nice/clear photos. Sometimes worn/damaged crystals obscure aging lacquer that makes the linen dials look much less nice.
Compare these two:
The one on the left was a little bit more silvery.
It is hard to accurately compare due to varying amounts of light in each photo, but the one on the right is more "white" and vibrant (in my opinion more desirable):
Hope this helps.
