Risho has white-colored and high thermal conductive materials especially for LED application. The color of this resin is white, so you can have a higher reflectivity from LED. This material also has a high thermal conductivity, so you can have a better heat transfer from LED.
White-Colored CCL with Glass Cloth with 1.3W/mK
Super White-Colored CCL with Silicone Base
Al-Base MCPCB with 1W/mK