Are black seed boxes best to start seeds.

[Bobberman]

I noticed that most seed trays are black. Is there a reason for that? Does the black plastic absorb the heat in the greenhouse better!

[TZ -OH6]

No practical reason. The soil mix is dark so that masks any color of the plastic. Larger containers (gallon pots on up) are a diffent matter in that the sun can hit the sides and warm them up, but they are often grown outside by nurseries.