Replace all the old half-life 2 texture files with the new ones 
by dragging them into your
half-life 2 directory:

hl2\materials\Models
episodic\materials\models
ep2\materials\models

Improved Alyx Vance texture have more ditail and color.
Face texture resolution: 1024x2048
Sheet texture resolution: 4096x4096
New realistic eyeballs & pupils

Alyx turned from an asian into an european. 
Her skin has gotten whiter and her eyes have more opened look.