The wolf is dark-skinned. الذِّئْبُ أَدْغَمُ‏.‏

Ibn Duraid said: The explanation of this is that wolves are dark-skinned whether they have lapped or not, and the darkness is inherent in them. It is sometimes said that they have lapped while hungry. This is said of someone who is envied for something they have not attained. And darkness also means blackness, and a dark-skinned man is called a *dughman*.
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This proverb is used to describe someone who is thought to have gained something good or beneficial, or who is envied for something they haven't actually obtained; that is, they are envied for something they don't possess.
A close English equivalent is:
“The grass is always greener on the other side.”
Meaning: People think others are better off than they actually are.
This is similar to the idea of ​​envy based on illusion.
“People envy what they only imagine.”
Meaning: People envy what they imagine, not what actually exists.
“Envy sees what isn't there.”
Meaning: Envy sees things that aren't there.
“All that glitters is not gold.”
Meaning: Not everything that looks good is gold.
This is similar to the reason for misguided envy.
“He is envied for blessings he never had.”
Meaning: He is envied for blessings he has never possessed.
The closest expression to the meaning of the Arabic proverb is:
“He is envied for what he does not possess.”
"He is envied for something he does not possess."
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قال ابن دُرَيْد‏:‏ تفسير ذلك أن الذئاب دُغْم وَلَغَتْ أو لم تَلَغ، والدُّغْمَة لازمة لها، فربما قيل قد ولغ وهو جائع‏.‏ يضرب لمن يُغْبَطُ بما لم يَنَلْه‏.‏
والدُّغْمَة‏:‏ السواد، والدُّغْمَانُ من الرجال‏:‏ الأسْوَدُ‏.‏