This is the 12510th most frequent Russian word.
колготок
"Колготок" is an informal or diminutive term for "tight" or "pantyhose."
The word "колготок" here is in the genitive plural form, indicating the presence of multiple tights as owned by the speaker.
У меня есть три пары колготок.
I have three pairs of tights.
"Колготки" is in the nominative plural form, referring to tights as the direct subject of the sentence.
Я купила новые колготки, чтобы носить с этим платьем.
I bought new tights to wear with this dress.
"Колготок" is in the genitive plural form again, used here to describe possession or association to the color property.