Grab the player damaged texture

from the link alongside

In the Player scene

Add a TextureRect as a child of Player

Rename it to DamageTexture

Add damage.png as the texture

In the Layout property

Set the Anchors Preset

To Full Rect

Create a New Animation

Call it take_damage

Set the animation duration to 0.4 seconds

Move to 0.4 on the timeline

Set the Scale to 1.5 and Key it

To make the texture fade

Move to 0.0 on the timeline

Select the DamageTexture node

In Visibility settings

Find Modulate and Key it

In the Player Script

In the Hitpoints set method

If the damage being done

is less than the remaining hitpoints

stop the damage animation then

start it again