The king of Octopuses has servants who have six, seven or eight legs. The distinguishing characteristics of the servants is that the one with seven legs always lie but the one with either six or eight legs speak the truth always.

On a certain night, four servants meet and converse:
The black one says, ‘We have 28 legs altogether.’
The green one says, ‘We have 27 legs altogether.’
The yellow one says, ‘We have 26 legs altogether.’
The red one says, ‘We have 25 legs altogether.’

Can you identify the color of the servant who is speaking the truth?