Yellow oddity in LED GU10 coloured lamps.

I saw some 3W GU10 LED lamps on ebay that were available in red, yellow, green and blue. I bought one of each along with some other lamps for fun.
They look good, but the yellow one is notable for being surprisingly bright and richly coloured for a yellow LED lightsource. The traditional yellow Gallium Arsenide LEDs always tend to look a bit dull and washed out. The LEDs were also notable for appearing yellow coloured when unlit leading me to guess that they might actually be a Gallium Nitride lightsource stimulating yellow phosphors. In this video I pop the lid on the yellow lamp and test the forward voltage of one of the LEDs to see which technology it uses.