Hen with blue colour on her cone

[Nela]

My hen is not doing well at all Leghorn just found her in the coop

 

[orelsi]

That's not enough information to help you. Take pictures if you can. What is she eating, including treats? How is her poop? Any abnormal behaviour? Wheezing? Fluid leaking from eyes, beak, vent, etc.

Blue comb is not necessarily a sign of illness. The tips and even more of the comb can get blue-ish due to temperature changes, especially cold weather, lack of vitamins, even excitement.