How do I fix some face's being light grey and others dark grey ?

Hey all i’m kinda new to blender but getting fairly good at it.
but ive been having problems in both my projects i’ve made so far…

it looks like 1 face is light grey and 1 face is dark grey i dunno if it makes a
different to the exported file but its really annoying while i’m editing!

In the 2 images under this text you can see what i mean…

Inconsistent face normals

Select all faces and Ctrl+N to recalculate the normals

ah ok … but now some have gone even darker grey (on the bottem) and the top ones are all normal again

hmm seemd to of half worked… the bottem face’s are now dark grey and on top they are light grey… :s

Blend file and screenshots ?

dont worry fixed it… had to click on the face’s then click the ‘inside’ button to get them to turn light grey again… so i think that fixed it?