As threatened: The Helgoland-class battleships, Germany's second dreadnought type and the last german capital ship with triple expansion engines. The speed difference to early turbine dreadnoughts was minimal, however, and the Helgolands were considered much better sea boats than their immediate predecessors too. With their powerful 50-caliber 305mm guns and their 300mm side armour, they were easily a match for all British dreadnoughts prior to HMS Orion, and still dangerous opponents for superdreadnoughts too.
Luckily for me, they all looked very similar to each other with minimal extermal differences. The class ship SMS Helgoland as she looked when she was completed:
SMS Helgoland had her funnels raised by 1,50 meters in 1915 and received observation posts on both masts; the forward searchlight platform had been extended aft, and the useless 88mm guns in the stern were removed.
At the time of the battle of Jutland, the aft compass pedestal had been removed, and the bridge structure had been enlarged. The canvas cover over the railings was always optional; since this picture shows SMS Helgoland at Jutland, the canvas is deployed.
The second ship of the class was SMS Thüringen. She differed from Helgoland only by having an additional ventilator between both forward funnels, otherwise she was identical.
Thüringen had her funnels heightened in a similar way as Helgoland, but already in 1913; otherwise, she received the same modifications as Helgoland. This is how she looked at Jutland, where she was credited by German sources with the destruction of HMS Black Prince.
Third and most prominent ship of her class was SMS Ostfriesland, although her fame mostly comes from her demise as a bombing target. The entire class is sometimes named for her, although she was neither laid down nor completed first. She had the same additional ventilator as Thüringen (probably; I've seen it only on a drawing, no phtograph I've ckecked shows that area sufficiently cleanly. This is how she looked at Jutland:
After Jutland, the torpedo nets and the remaining 88mm guns - save two in HA mountings - were removed and the galley exhaust was lengthened and stepped againt the after mast. She also had her funnels brought up to the same length as Helgoland and Thüringen and received an additional deckhouse just forward of the first funnel.
The last ship, SMS Oldenburg, initially looked identical to Thüringen. In 1913, she had her funnels heightened by 3 meters, thus having the highest funnels of the class.
And this is how she looked at Jutland:
As for the hull colour issue: I think the bright red rule is being not rigorously enforced since I joined the bucket (after all, most french, italian and russian ships have green hulls); in my opinion, we should just go for the real colour. Copying and pasting it should be easy enough even for a complete newcomer.