Depending on the size and type of stone (and common treatments), I like GIA, AGL, SSEF. GRS is also reputable. I am ok with AIGS for certain type of gemstones.
There are several labs with the name CGL, Which one are you referring to?
Ceylon Gem Lab?
Certified Gemological Laboratory of Europe
Central Gem Laboratory
CGL-GRS Swiss Canadian Gemlab
New to colored gems, is CGL & LGL cert. reliable for purchasing colored stones. Thx a lot~