Why is de used here instead of des?
I came across two sentences one right after the other. The first was:
"Elle a de grands yeux bleus."
The other was:
"Elle a des lèvres rouges."
Why is it not "Elle a des grands yeux bleues"? When I typed that it was counted wrong. Is "de" correct in this sentence because there is an adjective before the noun?
Yes, it is due to the placement of the adjectives. An adjective (or several) preceding a plural noun changes the partitive article des to de.
However, this rule doesn't apply when des is the contraction of "de + les" (= of/from/to the) as in :
Je suis jalouse des nouvelles bottes que tu as achetées
"I'm jealous of the new boots you bought."