You could continue with a thought related to the idea of the sky sometimes being red. Perhaps some information about that. Maybe a story that comes to mind.
Or you could continue with wordplay–writing that uses repetition and rhyme, for instance. You engage in wordplay when you let words to fly into your creation simply because they please you. “Making sense” takes a back seat.
After a few lines, pause and read over what you have written so far. Pick out a sentence or phrase that you like for any reason. Something five or six words long.
Skip a line and begin a new section by writing the sentence or phrase you just picked out. Continue for a few lines, any way that you like. Pause and reread everything. Pick out a new phrase that you like and begin the next section with it.
Keep going that way until you have almost filled the page. Stop before you get to the very end so that you can conclude with the sentence, “Sometimes the sky is red.”
Reread your work. Enjoy where the ramble of your writing has taken you. Draw or doodle on the page for a bit. Notice the connections between the sections. They might be deliberate or accidental. Think up a title that doesn’t have the words sometime, sky, or red in it.
Write the title at the top of the page. Put the date on your work as well.