Need help with image dimensions
Hey Dundee,
1/3 elements: the breaking point for mobile is 767, that is when they show full width. So your best bet would likely be to aim for images around 700 pixels wide.
Color sections: we would need to see the problem you are having, but in general I would suggest to use images which are at least 1500 pixels wide if they are going to be displayed full width. Likely higher if you want to make sure that they look good on larger screens as well.
Best regards,
Rikard