i have seen the flame colour of ws10 in pink in a j10b proto but these ones in blue??
since this is evidently a WS-10 variant, can we assume that the similiarily blue-flamed engine of the J-20 might not be a AL-31F derivate as previously assumed?
WS-10 AB used to be red-flamed, but now its blue, like the AL-31F. Maybe China has changed quite a few things on these engines, and has installed an improved WS-10 variant with hotter temperatures and more thrust (thus burning more blue-ish) in the J-20 long before?
NO ... the J-20 has the AL-31FN ! FACT !