A strange rendering with glass

Does this also happen without Ressource Pack?

Yes indeed

Without texture pack

This more-likely looks like there are two different kinds of stained glass. Replace the "bugged" glass blocks with the ones with correct color.

It changes nothing, the dark colour is still here

Confirmed for 14w17a

Confirmed for 14w18a

Confirmed for 14w18b

Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.

Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.

Ticket resolved as incomplete, because no answer in a reasonable amount of time (1+ year), if it still happens, please update the ticket.