They specifically called it out as a syntactical issue, where the issue was based around the requirement to have the 'red' or 'blue' keyword. The section on "2. The way you call a function depends on its color." makes this pretty explicit...

    2. The way you call a function depends on its color.

    Imagine a “blue call” syntax and a “red call” syntax. Something like:

    doSomethingAzure()blue;
    doSomethingCarnelian()red;

    When calling a function, you need to use the call that corresponds to its color.