"Pasty" refers to something that has a pale, sickly color, or something soft and doughy.
"Pallid" is the closest synonym, as it also means pale or lacking color, typically used to describe someone's complexion or appearance.
"Mold" (1) refers to a type of fungus or a shaped form, which is not related to the meaning of "pasty."
"Asphalt" (2) is a type of material used for roads and is unrelated to the idea of color or appearance.
"Spot" (4) refers to a small mark or location, which does not fit the meaning of "pasty."
Conclusion:
The word "pallid" is the correct synonym for "pasty," as both refer to a lack of color or a pale appearance.