what does winston see when he faces julia?

Isn't it that she is wearing makeup?

Yup, it's the makeup.

At the beginning of the chapter he sees her as pale.

Later, he sees her as a beautiful woman; her beauty is enhanced by make-up she bought.

Textual Evidence:

"He turned round, and for a second almost failed to recognize her. What he had actually expected was to see her naked. But she was not naked. The transformation that had happened was much more surprising than that. She had painted her face.

She must have slipped into some shop in the proletarian quarters and bought herself a complete set of make-up materials. Her lips were deeply reddened, her cheeks rouged, her nose powdered; there was even a touch of something under the eyes to make them brighter. It was not very skilfully done, but Winston's standards in such matters were not high. He had never before seen or imagined a woman of the Party with cosmetics on her face. The improvement in her appearance was startling. With just a few dabs of colour in the right places she had become not only very much prettier, but, above all, far more feminine. Her short hair and boyish overalls merely added to the effect. As he took her in his arms a wave of synthetic violets flooded his nostrils. He remembered the half-darkness of a basement kitchen, and a woman's cavernous mouth. It was the very same scent that she had used; but at the moment it did not seem to matter."

thank you to both of you :)