。
The grass is greener on the other side of the fence.
Literal
Next [of-の] grass [topic-は] ours [of-の] [than-より] blue-green.
A direct Japanese rendering of the English proverb. 隣の芝生は青い ('the grass next door is green') is a set proverb in Japanese, typically used with this exact wording. Note that 青い can mean both 'blue' and 'green' in traditional Japanese, especially for vegetation — a classic color-word oddity.