diff --git a/packages/vuetify/src/composables/theme.ts b/packages/vuetify/src/composables/theme.ts
index 541d38a17bd..94ff92dbd45 100644
--- a/packages/vuetify/src/composables/theme.ts
+++ b/packages/vuetify/src/composables/theme.ts
@@ -251,7 +251,8 @@ function genCssVariables (theme: InternalThemeDefinition, prefix: string) {
   const variables: string[] = []
   for (const [key, value] of Object.entries(theme.colors)) {
     const rgb = parseColor(value)
-    variables.push(`--${prefix}theme-${key}: ${rgb.r},${rgb.g},${rgb.b}`)
+    const colorVariable = rgb.a ? `${rgb.r},${rgb.g},${rgb.b},${rgb.a}` : `${rgb.r},${rgb.g},${rgb.b}`
+    variables.push(`--${prefix}theme-${key}: ${colorVariable}`)
     if (!key.startsWith('on-')) {
       variables.push(`--${prefix}theme-${key}-overlay-multiplier: ${getLuma(value) > 0.18 ? lightOverlay : darkOverlay}`)
     }