Ignore the colour, the XE also came with a black plug cover on later engines, although called a "redtop" in slang, they werent ever called so by vauxhall and hence vauxhall had no reason to stick to keeping the plug cover red.
The key thing is the SHAPE of the plug cover.
Xe one is like:
__________
|
Ecotec one is like:
__________
Take NO notice of colours at all.