I think that latex without ams does supply the theorem environment. I would like to make my own commands based on the built-in theorem functionality without using the ams tools package, so I can write the theorem name in colour. What can I do?
For instance, I would like "Definition" to be printed in orange. I would also like \theorem to print "Theorem" in orange as well.
\newtheorem{lexdefinition}{Definition}[section]
Use \color instead of \textcolor.
\documentclass{article}
\usepackage{xcolor}
\newtheorem{definition}{\color{orange}Definition}
\newtheorem{definitionnormal}{Definition}
\begin{document}
Some text preceding the definition.
\begin{definition}
A definition.
\end{definition}
Some text in the middle.
\begin{definitionnormal}
A definition.
\end{definitionnormal}
Some text to end the test.
\end{document}
I defined another environment just to see that the output is the same, except for the coloring.
amsthmand running\newtheorem{lexdefinition}{\textcolor{orange}{Definition}}[section]along with\let\oldthelexdef\thelexdefinition \renewcommand\thelexdefinition{\textcolor{orange}{\oldthelexdef}}?ams, building from the most basic latex built-in. But I would be fine taking basic code fromamsand use colour.