theme to a built-in name or a table, and swap it at any time with window:ChangeTheme(theme). Colours and numeric values tween across, so a live change feels intentional rather than abrupt; corner radii, fonts, and gradients apply instantly.
Built-in themes
Default
Cobalt
Ember
Amethyst
Frost
Rose
"default", "cobalt", "ember", "amethyst", "frost", or "rose".
Custom themes
A custom theme only sets the keys it needs. AtCreateWindow the rest fall back to the default. Strokes are the exception: set a fill and leave its stroke keys unset (ElementStroke, ElementStrokeGradient, ElementStrokeHover, TabStroke) and they are derived from that fill, so a colours-only theme still reads coherently. A later ChangeTheme with a partial table overlays the current theme instead — pass a built-in name to reset omitted keys. Any ColorSequence key also accepts a single Color3, which is widened to a flat gradient for you.
Theme keys
Window and shape
Window and shape
Text and fonts
Text and fonts
Tabs
Tabs
Elements
Elements
Controls
Controls