I don't know how or why, but as long as I have AW running, the vanilla clouds (they look like ones) overrides the clouds from resource pack that I use, which are a very subtle transparent, almost invisible.

What I did to reproduce the bug:

• To guarantee that nothing affected the test, I removed all content from minecraft directory and reinstalled MC from scratch.
• Installed MC 1.7.10.
• Installed the resource pack (if you want to try it yourself, just Aeon Main Pack is enough).
• Installed forge-1.7.10-10.13.4.1614.
• Installed OptiFine 1.7.10 HD U D1.
• Run the game. Result without AW:
  
• Installed Armourers Workshop 1.7.10 0.38.1.98
• Run the game. Result with AW:
  
  
• I have no other mod installed:
  

Now without OptiFine (that means, no Better Sky feature):

• With Forge only, no mods. Result:
  
• With Forge and AW, no other mods. Result:
  
• I have no other mod installed:
  

And as final test, I recovered my backup with forge, all mods, optifine, worlds etc, tested with and without AW: the same happens.

Tested with Clouds ON, Fancy.

It looks harmless :)

it looks Harmless :)

Except for resource pack maintainers. ;)

This was intentional, it only happens on valentines day and you can turn the holiday events off in the config file if you really don't want it.