diff --git a/Tests/LLVMTests/ANSIColor.swift b/Tests/LLVMTests/ANSIColor.swift
new file mode 100644
index 00000000..6e5737fa
--- /dev/null
+++ b/Tests/LLVMTests/ANSIColor.swift
@@ -0,0 +1,40 @@
+import Foundation
+
+/// Represents the possible ANSI color codes.
+enum ANSIColor: String {
+    case black = "\u{001B}[30m"
+    case red = "\u{001B}[31m"
+    case green = "\u{001B}[32m"
+    case yellow = "\u{001B}[33m"
+    case blue = "\u{001B}[34m"
+    case magenta = "\u{001B}[35m"
+    case cyan = "\u{001B}[36m"
+    case white = "\u{001B}[37m"
+    case bold = "\u{001B}[1m"
+    case reset = "\u{001B}[0m"
+    
+    func name() -> String {
+        switch self {
+        case .black: return "Black"
+        case .red: return "Red"
+        case .green: return "Green"
+        case .yellow: return "Yellow"
+        case .blue: return "Blue"
+        case .magenta: return "Magenta"
+        case .cyan: return "Cyan"
+        case .white: return "White"
+        case .bold: return "Bold"
+        case .reset: return "Reset"
+        }
+    }
+    
+    static func all() -> [ANSIColor] {
+        return [.black, .red, .green,
+                .yellow, .blue, .magenta,
+                .cyan, .white, .bold, .reset]
+    }
+}
+
+func + (left: ANSIColor, right: String) -> String {
+    return left.rawValue + right
+}
diff --git a/Tests/LLVMTests/ColoredStream.swift b/Tests/LLVMTests/ColoredStream.swift
new file mode 100644
index 00000000..84cfc4c6
--- /dev/null
+++ b/Tests/LLVMTests/ColoredStream.swift
@@ -0,0 +1,79 @@
+import Foundation
+
+/// Represents a stream that can write text with a specific set of ANSI colors
+protocol ColoredStream: TextOutputStream {
+    mutating func write(_ string: String, with: [ANSIColor])
+}
+
+extension ColoredStream {
+    /// Default conformance to TextOutputStream
+    mutating func write(_ string: String) {
+        write(string, with: [])
+    }
+}
+
+/// An output stream that prints to an underlying stream including ANSI color
+/// codes.
+class ColoredANSIStream<StreamTy: TextOutputStream>: ColoredStream {
+
+    typealias StreamType = StreamTy
+
+    var currentColors = [ANSIColor]()
+    var stream: StreamType
+    let colored: Bool
+
+    /// Creates a new ColoredANSIStream that prints to an underlying stream.
+    ///
+    /// - Parameters:
+    ///   - stream: The underlying stream
+    ///   - colored: Whether to provide any colors or to pass text through
+    ///              unmodified. Set this to false and ColoredANSIStream is
+    ///              a transparent wrapper.
+    init(_ stream: inout StreamType, colored: Bool = true) {
+        self.stream = stream
+        self.colored = colored
+    }
+
+    /// Initializes with a stream, always colored.
+    ///
+    /// - Parameter stream: The underlying stream receiving writes.
+    required init(_ stream: inout StreamType) {
+        self.stream = stream
+        self.colored = true
+    }
+
+    /// Adds a color to the in-progress colors.
+    func addColor(_ color: ANSIColor) {
+        guard colored else { return }
+        stream.write(color.rawValue)
+        currentColors.append(color)
+    }
+
+    /// Resets this stream back to the default color.
+    func reset() {
+        if currentColors.isEmpty { return }
+        stream.write(ANSIColor.reset.rawValue)
+        currentColors = []
+    }
+
+    /// Sets the current ANSI color codes to the passed-in colors.
+    func setColors(_ colors: [ANSIColor]) {
+        guard colored else { return }
+        reset()
+        for color in colors {
+            stream.write(color.rawValue)
+        }
+        currentColors = colors
+    }
+
+    /// Writes the string to the output with the provided colors.
+    ///
+    /// - Parameters:
+    ///   - string: The string to write
+    ///   - colors: The colors used on the string
+    func write(_ string: String, with colors: [ANSIColor]) {
+        self.setColors(colors)
+        stream.write(string)
+        self.reset()
+    }
+}
diff --git a/Tests/LLVMTests/FileCheck.swift b/Tests/LLVMTests/FileCheck.swift
index ca9affd6..9590140c 100644
--- a/Tests/LLVMTests/FileCheck.swift
+++ b/Tests/LLVMTests/FileCheck.swift
@@ -1224,16 +1224,34 @@ private struct CheckString {
   }
 }
 
-private enum DiagnosticKind {
+private enum DiagnosticKind: String {
   case error
   case warning
   case note
+
+  var color: ANSIColor {
+    switch self {
+    case .error: return .red
+    case .warning: return .magenta
+    case .note: return .green
+    }
+  }
 }
 
+struct StdOutStream: TextOutputStream {
+    mutating func write(_ string: String) {
+        print(string, terminator: "")
+    }
+}
+
+var stdoutStream = StdOutStream()
+var diagnosticStream = ColoredANSIStream(&stdoutStream)
+
 private func diagnose(_ kind : DiagnosticKind, _ loc : CheckLoc, _ message : String) {
-  print(message)
+  diagnosticStream.write("\(kind): ", with: [.bold, kind.color])
+  diagnosticStream.write("\(message)\n", with: [.bold])
   let msg = loc.message
   if !msg.isEmpty {
-    print(msg)
+    diagnosticStream.write("\(msg)\n")
   }
 }