I have used this answer from the question about how to design a beamer theme from scratch to design a Beamer theme to look like a university presentation (Powerpoint) template. There are 3 colour options for the Powerpoint template (blue,green,slate). I know one option for a solution would be to create 3 separate colour themes and to just call them with;
\usecolortheme{mythemeblue}
\usecolortheme{mythemegreen}
\usecolortheme{mythemeslate}
What I would like to do though is to define all the different colours in one colortheme file and then be able to use an option to call them as follows
\usetheme[blue]{mytheme} %or green or slate
I have seen questions on the site that seem to use \DeclareOption (at this question, but couldn't get to work) or \DeclareOptionBeamer (This question & This question - didn't really understand these solutions)
Ideally what I would like is a solution where I can define differently in the beamercolorthememytheme.sty the same colour names depending on what option was chosen. For example if option blue was chosen Beamer would know that \definecolor{col1}{RGB}{104,7,90} but if option green was chosen it would know that \definecolor{col1}{RGB}{81,139,36} etc
Hopefully this is enough info but if not let me know in the comments
This is what I have in my beamercolorthememytheme.sty
\mode<presentation>
% define colours from NUIG stylesheet
\definecolor{col1}{RGB}{104,7,90}
\definecolor{col2}{RGB}{27,65,99}
\definecolor{col3}{RGB}{138,167,147}
\definecolor{col4}{RGB}{143,183,195}
\definecolor{col5}{RGB}{194,230,242}
% set colours for different elements
\setbeamercolor{structure}{fg=col3!100!col4}
\setbeamercolor{frametitle}{bg=col4,fg=col2}
\setbeamercolor*{title page header}{fg=col5}
\setbeamercolor*{subtitle}{fg=col5}
\setbeamercolor*{author}{fg=col5}
\setbeamercolor*{date}{fg=col5}
\setbeamercolor*{item}{fg=col5}
\setbeamercolor{block title}{bg=col1,fg=col5}
\mode
<all>

\else%and\fi%when trying to add a third option. All working fine now. – gman Feb 19 '16 at 20:13