because the date has passed already, so that box shows as red.

If you were EFiling the return today, you wouldnt be able to schedule the 1st estimated, since the date has passed...thats why it shows as red, after June 16th the first 2 boxes will show red, after Sept 15th the first 3 boxes would show red and so on..

Sounds like it isn't an error to me.

When the return has not been filed yet I agree. I believe it is an error when the return has already been filed prior to April 15th. I believe those also show as an error.

its just due to the date being past, yes it shows as a red error, its an error that doesn't matter though.

You are right. It doesn't matter. However, it is another example of poor programming in the software. Seeing that red X does make you check that you didn't screw up on an unfiled return.