The Blue-winged Grasshopper (Oedipoda caerulescens) is a light brown grasshopper with often dark barred forewings and legs. 
The hindwings are strikingly blue, which is immediately noticeable when it flies away.
The Blue-winged Grasshopper looks very similar to the Blue-winged Sand Grasshopper (Sphingonotus caerulans) and can easily be confused with it. 
However, the hindwings of the Blue-winged Grasshopper are brighter blue and the wings extend less far beyond the tip of the abdomen. 
The Blue-winged Sand Grasshopper generally has a more southern distribution area in Europe than the Blue-winged Grasshopper.

Another very similar species is the Red-winged Grasshopper (Oedipoda germanica), which, however, is easily distinguished by its red wing color.

Brucherbierg-Lallengerbierg Nature Reserve, Luxembourg, 12 August 2024