I noticed this.
All are dry accept the more dark colored line.
Is that a seal problem??

Click image to enlarge

Can you smell any fuel?

If youre worried take the shield off and try nip the nut up a bit more. From memory there is no rubber seal on those it's just a flared fitting from when I did my inlet manifold. Current 2007 TDV8 Vogue Buckingham Blue

No fuel smell.
Is it hard to remove the shield? 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k

To remove the shield it's fiddly for sure. I can't remember if you can get to the fuel rails from the top which is much easier to remove bits. If you've got a crows foot spanner you might get it in there. To be fair it doesn't look like there is any issue really especially if there is no fuel smell so if it was me if I'd clean it leave it and see if it looks like it's getting wet again Current 2007 TDV8 Vogue Buckingham Blue

 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k