He's talking about the idea of "painting the town red".
"But taking the case of ordinary pagan recklessness and pleasure seeking, it is, as we have said, well expressed in this image. First, because it conveys this notion of filling the world with one private folly; and secondly, becuase of the profound idea involved in the choice of colour. Red is the most joyful and dreadful thing in the physical universe; it is the fiercest note, it is the highest light, it is the place where the walls of this world of ours wear thinnest and something beyond burns through. It glows in the blood which sustains and in the fire which destroys us, in the roses of our romance and in the awful cup of our religion. It stands for all passionate happiness, as in faith or in first love.
"Now, the profligate is he who wishes to spread this crimson of conscious joy over everything; to have excitement at every moment; to paint everything red. He bursts a thousand barrels of wine to incarnadine the streets; and sometimes (in his last madness) he will butcher beassts and men to dip his gigantic brushes in their blood. For it marks the sacredness of red in nature, that it is secret even when it is ubiquitous, like blood in the human body, which is omnipresent, yet invisible. A s long as blood lives it is hidden; it is only dead blood that we see. But the ealier parts of the rake's progress are very natural and amusing. Painting hte town red is a delighful thing until it is done. It would be splendid to see the cross of St. Paul's as red as the cross of St. George, and the gallons of red paint running down the dome or dripping from the Nelson Column. But when it is done, when you have painted the town red, an extraordinary thing happnes. You cannot see any red at all.
"I can see, as in a sort of vision, the successful artist standing in the midst of that frighful city, hung on all sides with the scarlet of his shame. And then, when everything is red, he will long for a red rose in a green hedge and long in vain; he will dream of a red leaf and be unable even to imagine it. He has desecrated the divine colour, and he can no longer see it, though it is all around. I see him, a single black figure against the red-hot hell that he has kindled, where spires and turrets stand up like immobile flames: he is stiffened in a sort of agony of prayer. Then the mercy of Heaven is loosened, and I see one or two flakes of snow very slowly begin to fall."
It makes me think of one of my favorite lines from Macbeth: "Will all great Neptune's ocean wash this blood clean from my hand? No, this my hand will rather the multitudinous seas incarnadine, making the green one red."
Which quote, in turn, reminds me that a "little yeast works through the whole batch of dough." To interpret on the flip side of usual, a splash of color, in the right place, brightens all of life. I stand by my beautiful red sheets.