Spelling
    Tools -> Options -> Composition  Check the box 'Check spelling 
before sending'
Signature
   
http://kb.mozillazine.org/Signatures_%28Thunderbird%29
Attachements
When an email has an attachement at the bottom of the TBird window there 
is an icon like a PAPERCLIP.  Click on this. On the RH side there will 
be an option to 'Save all'.
I set my default font to be Calibri. When I opened the 'reply' I got 
Calibri.
Regarding the colour, what does the setting in
  Tools->Composition->General->Send Options : Text Options say. Mine is 
set to 'Send in both plain text and HTML'. So you should see
Blue on Green apart from this last bit.
On the email input bod there are two overlapping squares next to the 
font label
The toolbat underneath the Subject line on mine goes
Body Text   Font (calibri)  Overlapping squares. If you click on these 
you can cgange the text colour (the upper one) or the vackground (the 
lower one)
These will override those set in Tools>Composition->General  TEXT color 
& Backbround Color.
IF you are sending email in HTML format.
Samantha
--
Please post to: Hampshire@???
Web Interface: 
https://mailman.lug.org.uk/mailman/listinfo/hampshire
LUG URL: 
http://www.hantslug.org.uk
--------------------------------------------------------------