Logic puzzle: Which octopus is telling the truth?

King Octopus has servants with six, seven, or eight legs. The servants with seven legs always lie, but the servants with either six or eight legs always tell the truth.

One day, four servants met.
The blue one says, “Altogether, we have 28 legs.”
The green one says, “Altogether, we have 27 legs.”
The yellow one says, “Altogether, we have 26 legs.”
The red one says, “Altogether, we have 25 legs.”

What is the colour of the servant who tells the truth?

Hint: since they all disagree, at least three are lying. How many legs does that account for?

Well The Green one?

Since the four are disagreeing then $3$ must be lying. Since only octopuses with 7 legs lie then there must be $7\times3 = 21$ legs.

That leaves the honest octopus with either $6$ or $8$ legs. So the total number of legs should either be $21+6= 27$ legs or $21+8=29$ legs.

Since no one says that they have $29$ legs then only the Green octopus is saying the truth.

It seems to be simple unless I missed something in the riddle.