Absolutely true.

Pictures were taken of von Richthofen's corpse, funeral, and gravesite. These photographs were then dropped over German positions and aerodromes.

While in many ways, this could be taken as a tribute to the pilot, it was also done to prove that the Red Baron was indeed dead. Further, the pictures prevented any propaganda claims Germany may have made regarding his still being alive, or having been treated like a common enemy.

Instead, he was given a full, respectful miltary burial. Indeed, Allied squadrons based nearby presented wreaths at the funeral, one of which was enscribed "To Our Gallant and Worthy Foe." Which is not to say that this was universally applauded... more than a few Allied flying officers were rather vexed that he was given such honors.

So indeed, the Allies did drop a tribute of sorts to the Red Baron over the German lines.