I got a sample of the beige. But I decided to go with the grey, don't recall what RD calls that one, it's the lighter grey. I also have some darker tiles in a couple areas. The grey is probably about the same as the beige would be as far as your question. I have worked on my floor with the tiles installed for several months now, including a very rainy season. The approach to the garage is dirt, so that means some mud on my shoes, though not a lot due to the type soil we have. Anyway, yes, the grey tiles show the dirt slightly more than my darker tiles. Not as much as I had expected, but some. The grey tiles I have are all FreeFlow, the open-lattice style. I have found that every couple weeks, during that rainy spell, I was able to clean the tiles by simply spraying them towards the door with the garden hose. No scrubbing or mopping needed. At least, so far.
While I am at it, I also have just yesterday run the shop vac over the FreeFlows. I had been running a table saw, and doing some drilling in steel and aluminum, etc., so I had sawdust and some fine steel bits and so forth down under the tiles. Plus a few bits of grass, dog hair, etc. The shop vac removed anything I can see down in there with a single pass of the hose attachment. No problem.