I want to color simple functional groups in organic molecules using the chemfig package. I've come up with a solution that achieves what I want (MWE), but I find it very cumbersome. I thought it could be possible to wrap an entire group in one single color-statement. This question about colouring the background of a group of atoms in chemfig also gives a neat graphical emphasis of a group of atoms.

Is my solution, and the solution to the question above, the easiest way to colour or mark groups of atoms (including bonds) in chemfig? Just now, I don't have a need to easily reproduce loads of coloured functional groups, but I would like to know if there are easier ways to solve this problem without predefining macros for each group.

I believe I understand that the underlying problem is the way chemfig uses TikZ nodes to draw the structures, but I can't help to think that there should be a way to define some color environment that applies to all the TikZ nodes made by chemfig.




    \chemfig{H-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-{\color{blue}C}(=[1,,,,blue] {\color{blue}O})(-[7,,,,blue] {\color{blue}OH})}


enter image description here

  • I don't really have an answer but I'd probably really define macros or submols (depending on the wanted functionality)
    – cgnieder
    Feb 21, 2015 at 18:50
  • I believe that what you did is the best you can do in chemfig at the moment.
    – pisoir
    Feb 25, 2015 at 6:59

1 Answer 1


Relate to this post.

    \chemfig{H-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)(-[,,,,draw=none]\RED)([,,,,,red]-[,,,,black]C(=[1]O)(-[7]OH))}\BLACK \\[1cm]


  • [,,,,red] is to set the color of bonds within COOH.
  • [,,,,black] is to set the color of bond between C2H5 and COOH.
  • (-[,,,,draw=none]\RED) is to create an ad hoc atom to change the color.
    • you can change the color anywhere, but sometimes it may cause bad spacing/positioning.
    • (e.g. chemfig reads \RED COOH as five atoms, with the first atom having zero width.)

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