diff --git a/CHANGELOG.md b/CHANGELOG.md
index 129b840..daa450e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- add `set_alpha` filter
+
+
 ## [2.3.0](https://github.com/InioX/matugen/compare/v2.2.0...v2.3.0) - 2024-05-29
 
 ### Added
diff --git a/example/colors.whatever-extension b/example/colors.whatever-extension
index 8bcc5f7..63a4e3b 100644
--- a/example/colors.whatever-extension
+++ b/example/colors.whatever-extension
@@ -22,4 +22,8 @@ source_color {{colors.source_color.default.hex}};
 
 <* for name, value in colors *>
     {{name | replace: "_", "-" }} {{value.default.hex}};
-<* endfor *>
\ No newline at end of file
+<* endfor *>
+
+Only works with rgba and hsla
+{{ colors.source_color.default.rgba | set_alpha 0.5 }}
+Output: rgba(r, g, b, 0.5)
diff --git a/src/util/color.rs b/src/util/color.rs
index a5b0a5d..fbef8bc 100644
--- a/src/util/color.rs
+++ b/src/util/color.rs
@@ -64,6 +64,16 @@ pub fn format_rgba(color: &Rgb) -> String {
     )
 }
 
+pub fn format_rgba_float(color: &Rgb) -> String {
+    format!(
+        "rgba({:?}, {:?}, {:?}, {:.1})",
+        color.red() as u8,
+        color.green() as u8,
+        color.blue() as u8,
+        color.alpha()
+    )
+}
+
 pub fn format_hsl(color: &Hsl) -> String {
     format!(
         "hsl({:?}, {:?}%, {:?}%)",
@@ -83,6 +93,16 @@ pub fn format_hsla(color: &Hsl) -> String {
     )
 }
 
+pub fn format_hsla_float(color: &Hsl) -> String {
+    format!(
+        "hsla({:?}, {:?}%, {:?}%, {:.1})",
+        color.hue() as u8,
+        color.saturation() as u8,
+        color.lightness() as u8,
+        color.alpha()
+    )
+}
+
 pub fn get_color_distance_lab(c1: &str, c2: &str) -> f64 {
     let c1 = Lab::from(Argb::from_str(c1).unwrap());
     let c2 = Lab::from(Argb::from_str(c2).unwrap());
diff --git a/src/util/filters.rs b/src/util/filters.rs
index b21d0b8..91b07c2 100644
--- a/src/util/filters.rs
+++ b/src/util/filters.rs
@@ -1,3 +1,4 @@
+use colorsys::ColorAlpha;
 use colorsys::ColorTransform;
 use colorsys::Hsl;
 use colorsys::Rgb;
@@ -7,7 +8,8 @@ use upon::Value;
 use crate::util::template::{check_string_value, parse_color};
 
 use crate::util::color::{
-    format_hex, format_hex_stripped, format_hsl, format_hsla, format_rgb, format_rgba,
+    format_hex, format_hex_stripped, format_hsl, format_hsla, format_hsla_float, format_rgb,
+    format_rgba, format_rgba_float,
 };
 
 pub fn set_lightness(value: &Value, amount: f64) -> Result<String, String> {
@@ -67,3 +69,37 @@ pub fn set_lightness(value: &Value, amount: f64) -> Result<String, String> {
         v => Ok(v.to_string()),
     }
 }
+
+pub fn set_alpha(value: &Value, amount: f64) -> Result<String, String> {
+    let string = check_string_value(value).unwrap();
+
+    let format = parse_color(string);
+
+    debug!("Setting alpha on string {} by {}", string, amount);
+
+    if format.is_none() {
+        return Ok(string.to_string());
+    }
+
+    if !(0.0..=1.0).contains(&amount) {
+        return Err("alpha must be in range [0.0 to 1.0]".to_string());
+    }
+
+    match format.unwrap() {
+        "hex" => Err("cannot set alpha on hex color".to_string()),
+        "hex_stripped" => Err("cannot set alpha on hex color".to_string()),
+        "rgb" => Err("cannot set alpha on rgb color, use rgba".to_string()),
+        "rgba" => {
+            let mut color = Rgb::from_str(string).unwrap();
+            color.set_alpha(amount);
+            Ok(format_rgba_float(&color))
+        }
+        "hsl" => Err("cannot set alpha on hsl color, use hsla".to_string()),
+        "hsla" => {
+            let mut color = Hsl::from_str(string).unwrap();
+            color.set_alpha(amount);
+            Ok(format_hsla_float(&color))
+        }
+        v => Ok(v.to_string()),
+    }
+}
diff --git a/src/util/template.rs b/src/util/template.rs
index cae13ba..5c77049 100644
--- a/src/util/template.rs
+++ b/src/util/template.rs
@@ -12,7 +12,7 @@ use upon::Value;
 
 use crate::util::color;
 use crate::util::color::color_to_string;
-use crate::util::filters::set_lightness;
+use crate::util::filters::{set_alpha, set_lightness};
 use crate::util::variables::format_hook_text;
 
 use std::fs::canonicalize;
@@ -302,6 +302,7 @@ fn export_template(
 
 fn add_engine_filters(engine: &mut Engine) {
     engine.add_filter("set_lightness", set_lightness);
+    engine.add_filter("set_alpha", set_alpha);
     engine.add_filter("to_upper", str::to_uppercase);
     engine.add_filter("to_lower", str::to_lowercase);
     engine.add_filter("replace", |s: String, from: String, to: String| {