About:

When writing with the command "/execute if blocks," and using the "all" argument, anything that goes beyond the basic arguments of the command are highlighted in red, even if the arguments that come after are correct.

Example:

"/execute if blocks ~ ~ ~ ~ ~ ~ ~ ~ ~ all run say hi"

In the example command, the sub-args after "all" would be highlighted in red. However, the command would run just fine as if there were no errors.

In another case scenario, if you were to write this example command instead:

"/execute if blocks ~ ~ ~ ~ ~ ~ ~ ~ ~ masked run say hi"

It would say the command is formatted properly, and no text would be highlighted in red.