Depends on how you want to use the colors etc. What I have found works really well is to have a list of HTML Hex Colors saved in an expression code fragment. You can then give the colors a variable name so that when you are building your HTML email templates you can replace the color value with the value from the fragment. i.e.
{% let BrandPrimary = FF0000 %}
{% let BrandSecondary = 002395 %}
Then in your HTML can you do include the fragment in your template and call in the different colors by names.
<style>
.div-1 {
background-color: #{{BrandPrimary}};
}
.div-2 {
background-color: #{{BrandSecondary}}; }
</style>
<body>
<div class="div-1">Something </div>
<div class="div-2"> something else </div>
</body>
https://experienceleague.adobe.com/en/docs/journey-optimizer/using/content-management/personalizatio...
Then if you need to update the color definitions or add/change them you can do it in one place, within the fragment and have it apply everywhere the fragment is used.
