The built-in catalogue covers a lot of ground, but sometimes you want your own palette: brand colours, a house diagram style, or a notation of your own. Custom themes let you author exactly that, save it, and reuse it. A saved custom theme behaves just like a built-in one: pick it on a tab and new elements adopt its colours. Custom themes work for everyone, signed in or not, so the canvas keeps working without a sign-in.
Building a theme
You build a theme from the Custom category in the Tab Appearance Theme tab. Choose + New theme to open the theme builder. It is fast by default and deep on demand:
Start with three colours: a Base for the canvas background, a Fill for element fill, and a Stroke for outlines, plus a name. From just these three, livediagram derives sensible defaults for everything else, so a usable theme exists after three clicks.
Expand Customize details for the granular controls: text colour, a background pattern picker, and a pattern colour.
Expand the per-shape colours section, an advanced option, to give each shape kind its own fill, border, and text, which is how you reproduce a notation like "diamonds are amber".
A live preview shows a few sample shapes in your in-progress theme, rendered the same way the canvas would, so you see the result before saving. Save stores the theme and applies it to the active tab.
Saving and reusing
Custom themes are tied to your account and listed under the Custom category wherever you pick a theme: the Tab Appearance dialog and the new-diagram template picker both show them, so you can apply or author one the moment you start a diagram. If you sign up after creating themes as a guest, they carry over to your account.
Managing your themes
The Explorer has a Themes entry under its Library section where you can manage them all in one place: each is shown as a preview card you can Edit, Duplicate, or Delete.
Editing and deleting
Editing a theme opens the same builder again. Deleting one is safe for diagrams that still reference it: they fall back to the default look and keep rendering rather than breaking. If you delete a theme that the diagram you have open is using, that tab reverts to the default theme straight away so the change is visible.
To tweak a built-in theme, start a new custom theme from the same colours and edit from there. The shipped catalogue stays read-only, so your edits never touch the originals.
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