# Color highlighting text and environments in LyX

I am using LyX 2.0.5 with document class `article` and 'Theorems (AMS)' in the modules. I am wondering if it is possible to make it so that the titles of different environments will be highlighted in different colors ("highlighted" in the sense of a highlight marker. I.e., having a colored background, w/o changing the font color). E.g., in the `Theorem` environment the words Theorem 12.1 will be typeset with red highlight, in the `Definition` environment the words Definition 5.9 will be typeset with yellow highlight, etc.

I am guessing the will require changing the module?

(Note: there are parts of this solution that are sub-optimal, and I'm aware of that, but I'll have to fix that later. I'll remove this note when I find the time to improve things.)

You can change the files `theorems-ams.module` and `theorems-ams.inc`, or better create copies as described in my answer to How to make "claim" environments look like "theorem" environment?

In `theorems-ams.module`, add `xcolor` to the required packages. I.e. where it says

``````Requires    amsmath,amsthm
``````

edit this to

``````Requires    amsmath,amsthm,xcolor
``````

(This bit is untested, but I assume it will work.)

In `theorems-ams.inc`, find the style you want to change, for example the block defining the look of theorems starts with `Style Theorem`.

In the `Style` block there is a sub block `Preamble`, which by default looks like

``````Preamble
\theoremstyle{plain}
\newtheorem{thm}{\protect\theoremname}
EndPreamble
``````

Using code taken from egreg's answer to amsthm environment and colorbox, edit this to read

``````Preamble
\newtheoremstyle{Coloredtheo}%
{3pt}    %Space above
{3pt}    %Space below
{}   %Body font
{}   %Indent amount
{\colorbox{red}{\color{black}\thmname{#1}%
\thmnumber{\@ifnotempty{#1}{ }\@upn{#2}}}%
\thmnote{ {--- \the\thm@notefont#3.}}%
Note that this will not change the view in LyX, only in the PDF. Do similarly for `Definition`, but use a different name for the `\newtheoremstyle`. The background colour is set by the first argument to `\colorbox`, here `red`.
For a single document, you could use the Local layout under Documents --> Settings. Add the entire `Style` block to the local layout. You may need to also include `\usepackage{xcolor}` to the `Preamble` block.
• Amazing! One little thing though: The dot that usually appears after the theorem number is gone. I tried changing `{}` to `{.}` in the `%Punctuation`, but this adds the dot outside of the color box. – doodle Mar 26 '14 at 23:27
• OK, got it. I changed `\@upn{#2}}` to `\@upn{#2}}{.}` in your code. That took care of that dot. // Also, I kept the `Color Red` parameter under `Label Font`, which you mentioned before your edit. It's not what I was looking for as far as end result in the PDF, but it does make LyX look slightly more like the PDF. Thanks again! – doodle Mar 26 '14 at 23:47