Hi there, this is the original way Chris plays the song on the guitar. At least in 
the AOL sessions from 2003.

Since I dont know the name of the chords I will give you them here for the 
beginning, sorry for that...
Figured the chords out from the Session at AOL of the song
(search on youtube "Warning Sign - Coldplay Live Sessions @ AOL", gorgeous 240p video!)
garvmg from coldplaying.com helped me with the guitar tuning!

Tune your guitar the following:
EADGBD (high e string 2 steps down from E to D)
Capo 2nd fret!


Start: C 3.3.2.0.1.0    C# 3.3.0.0.1.0

Verse:                  Chorus:                    End:
C 3.3.2.0.1.0           C 3.3.2.0.1.0              G 10.10.9.0.8.0
B 8.8.7.0.6.0           Em 0.2.2.0.0.0             B 8.8.7.0.6.0
G 10.10.9.0.8.0         G# 3.2.0.0.3.0             F# 1.3.3.2.1.0
D 5.5.4.0.3.0           D# 0.0.0.2.3.0             Em 0.2.2.0.0.0


Here comes the Song:
-------------------------------------------------------------------------

C/C# (C most of the time, C# very shortly, just a finger lift from the third fret, 
see the video for the idea!)

B C G D      x4

    B       C
  A warning sign
G             D                     B    C
  and I missed the good part and I realised
G           D                     B      C
  that I started looking and the bubble burst
G           D                  B    C    G    D
  when I started looking for excuses

Come on in
and I ve got to tell you what a state I m in
yes I ve got to tell you in my loudest tones
that I started looking for a warning sign    
(continue on D here for a few seconds, then chorus!)

Chorus:
           C         Em
When the truth is
    Ab        Eb
I miss you
        C            Em
yeah the truth is
        Ab       Eb
that I miss you so

A warning sign
you came back to haunt me and I realised
that you were an island and I passed you by
when you were an island to discover

Come on In
and I ve got to tell you what a state I m in
yes I ve got to tell you in my loudest tones
that I started looking for a warning sign

Chorus:
When the truth is
I miss you
yeah the truth is
that I miss you so...
        C        Em
and I m tired
                  Ab      Eb
I should not have let you go...


G  B  F#  Em     x2

     G     B              F#   Em
So I crawl back into your open arms      x4