diff --git a/tw-macro/src/lib.rs b/tw-macro/src/lib.rs
index 1c42977..a4eb1c9 100644
--- a/tw-macro/src/lib.rs
+++ b/tw-macro/src/lib.rs
@@ -208,17 +208,17 @@ fn parse_u8(input: &str) -> IResult<&str, u8> {
     Ok((input, num as u8))
 }
 
-// rgb(255, 255, 255)
+// rgb(255, 255, 255) rgb(255_255_255)
 fn parse_rgb_color(input: &str) -> IResult<&str, String> {
     let (input, _) = tag("rgb(")(input)?;
     let (input, _) = multispace0(input)?;
     let (input, r) = parse_u8(input)?;
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag(",")(input)?;
+    let (input, _) = alt((tag(","), tag("_")))(input)?;
     let (input, _) = multispace0(input)?;
     let (input, g) = parse_u8(input)?;
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag(",")(input)?;
+    let (input, _) = alt((tag(","), tag("_")))(input)?;
     let (input, _) = multispace0(input)?;
     let (input, b) = parse_u8(input)?;
     let (input, _) = multispace0(input)?;
@@ -227,21 +227,21 @@ fn parse_rgb_color(input: &str) -> IResult<&str, String> {
     Ok((input, color))
 }
 
-// rgba(255, 255, 255, 0.5)
+// rgba(255, 255, 255, 0.5) rgba(255_255_255_0.5)
 fn parse_rgba_color(input: &str) -> IResult<&str, String> {
     let (input, _) = tag("rgba(")(input)?;
     let (input, _) = multispace0(input)?;
     let (input, r) = parse_u8(input)?;
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag(",")(input)?;
+    let (input, _) = alt((tag(","), tag("_")))(input)?;
     let (input, _) = multispace0(input)?;
     let (input, g) = parse_u8(input)?;
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag(",")(input)?;
+    let (input, _) = alt((tag(","), tag("_")))(input)?;
     let (input, _) = multispace0(input)?;
     let (input, b) = parse_u8(input)?;
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag(",")(input)?;
+    let (input, _) = alt((tag(","), tag("_")))(input)?;
     let (input, _) = multispace0(input)?;
     let (input, a) = number::complete::double(input)?;
     let (input, _) = multispace0(input)?;
@@ -356,6 +356,7 @@ fn arbitrary_opacity(input: &str) -> IResult<&str, ()> {
             )))
         }
     };
+    let (input, _) = opt(tag("%"))(input)?;
     let (input, _) = tag("]")(input)?;
     Ok((input, ()))
 }