How to reproduce:
1. Create a new HDRP Project
2. In the Project Window, create a new PBR Shader graph
3. In the Master Node, change the Surface to "Transparent", colour to Red and the Smoothness to 1
4. Save the shader, apply it to a material and a then to a Cube game object
5. Observe the Cube object

Expected result: The resulting material is very clearly red
Actual result: The resulting red colour is bleached in the HDRP project only, LWRP works as expected

Reproduced in: 3.3.0, 3.1.0
Not Reproducible: 3.0.0

Note: Version 3.0.0 seems to work similarly to LWRP on Objects in the Scene but not in the Shadergraph window

Fixed in: 2018.3.0b4