Why are early Spring flowers predominantly yellow?

Possibly to be more noticable to insects after winter for pollination .Just a guess :)

What an interesting question, Aster could well be right. We always thought of it as coming out of the gloom into a new spring and summer. The rising of the sun.
I have already seen Primroses out, to me the best first flowers, although Daffodils are commonplace now.

I'm glad you asked that even though I don't know the answer (I think the pollinating insects theory sounds plausible). I noticed the same a couple of springs ago and wondered why.

Yes, i think it must be the insect thing too. (they always make a beeline - HA! - for any bright yellow clothing if you notice)
Always seems to me that there is a lot of yello, and a lorra, lorra mauve/purple, and i don't like the combination of the 2, i have to say. Clearly the insects are not fussed, and they matter more on this point!
I do like "proper" ie mid blue flowering plants, which are harder to come by, and RED, all shades of.

There are lots of theories about whether animals and insects can see colours.
It's the warmer weather that brings animals and insects out of hibernation and they are attracted by scent, whether it be flowers or seeds germinating under the ground.

you could b right, but why do they definitely prefer yellow T-shirts then?!

I really don't know the answer to that one, except it may just be it's a very light colour.
It may just be you smell really nice Weeding.
Am sending you another PM. this morning.