What factors are likely to determine whether a specific plant species bothers to be heliotropic (i.e. track the Sun in its daily East-to-West passage)? For example, the Alpine Buttercup and the Sunflower do, but blades of grass seem to lie at random although, being all leaf, they would seem to have most to gain.

(This question prompted by an ironic Anonymous reply to the question on lime and lemon buoyancy "I think I'll go watch some grass grow now and speculate with friends about why the blades face this way or that", which itself leads to 2 comments: (a) I'm not the one posting to TLW at 03:40; and (b) Since when does TLW accept anonymous postings?)

Do we all perceive color the same way ? for example do we all see the same color green or is the word green or red or blue just names to tag how we perceive those color. If I switched eyes with someone he might see the grass the same way as I perceive the sky but still call it green even though for me it would be blue.

The same goes for colorblind people (those unfortunate to mix up colors) if they were brought up seeing the grass as we would see it red. He would say green to everything red if we were able to see through his eyes. It would rely on education then.

Do I make sense ?