This is the 670th most frequent Slovenian word.
isti
"isti" = "the same"
The word 'isti' (same) is used here as an adjective to emphasize that the cyclist being referred to is identical to the one mentioned in the previous context.
To je isti kolesar, ki je včeraj zmagal na dirki.
This is the same cyclist who won the race yesterday.
The word 'isto' (same) acts as an adverb-like pronoun modifying 'barvo,' specifying that the color chosen by everyone is identical.
Vsi so izbrali isto barvo za zidove.
Everyone chose the same color for the walls.
'Isti' (same) is used as an adjective describing 'telefon,' indicating that the phone's type or model is identical to the speaker's.