diff --git a/.nix/catala.nix b/.nix/catala.nix
index 6ecffc6f..186620c7 100644
--- a/.nix/catala.nix
+++ b/.nix/catala.nix
@@ -25,6 +25,7 @@
 , zarith_stubs_js
 , ocaml-crunch
 , cohttp-lwt-unix
+, ocolor
 }:
 
 buildDunePackage {
@@ -62,6 +63,7 @@ buildDunePackage {
     zarith
     zarith_stubs_js
     cohttp-lwt-unix
+    ocolor
   ];
 
   # Currently there is no unit tests in catala and Cram tests are handled by clerk
diff --git a/.nix/ocolor.nix b/.nix/ocolor.nix
new file mode 100644
index 00000000..4157841d
--- /dev/null
+++ b/.nix/ocolor.nix
@@ -0,0 +1,39 @@
+{ lib
+, buildDunePackage
+, odoc
+, cppo
+, ounit
+, fetchurl
+}:
+
+buildDunePackage rec {
+  pname = "ocolor";
+  version = "1.3.0";
+  
+  minimumOCamlVersion = "4.11";
+
+  src = fetchurl
+    {
+      url = "https://github.com/marc-chevalier/${pname}/archive/${version}.tar.gz";
+      sha256 = "sha256-V7xuBRNbWWi3OpDRe7WakOO4Vz6nyoV8/gyn45fpmYA=";
+    };
+
+  duneVersion = "3";
+
+  propagatedBuildInputs = [
+    odoc
+    ounit
+    cppo
+  ];
+
+  nativeBuildInputs = [ cppo ];
+  doCheck = true;
+
+  meta = with lib; {
+    homepage = "https://github.com/marc-chevalier/ocolor";
+    description =
+      "OColor is an OCaml library which help to format nicely using ANSI escape codes.";
+    license = licenses.mit;
+    maintainers = [ ];
+  };
+}
diff --git a/.nix/packages.nix b/.nix/packages.nix
index c4490d5a..26c25e75 100644
--- a/.nix/packages.nix
+++ b/.nix/packages.nix
@@ -11,4 +11,5 @@ ocamlPackages.overrideScope' (self: super: {
   ubase = self.callPackage ./ubase.nix { };
   dates_calc = self.callPackage ./dates_calc.nix { };
   french_law = self.callPackage ./french_law.nix { };
+  ocolor = self.callPackage ./ocolor.nix { };
 })
diff --git a/flake.lock b/flake.lock
index c30d09e8..c6adec9f 100644
--- a/flake.lock
+++ b/flake.lock
@@ -5,11 +5,11 @@
         "systems": "systems"
       },
       "locked": {
-        "lastModified": 1681202837,
-        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
+        "lastModified": 1689068808,
+        "narHash": "sha256-6ixXo3wt24N/melDWjq70UuHQLxGV8jZvooRanIHXw0=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
+        "rev": "919d646de7be200f3bf08cb76ae1f09402b6f9b4",
         "type": "github"
       },
       "original": {
@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1684049129,
-        "narHash": "sha256-7WB9LpnPNAS8oI7hMoHeKLNhRX7k3CI9uWBRSfmOCCE=",
+        "lastModified": 1690640159,
+        "narHash": "sha256-5DZUYnkeMOsVb/eqPYb9zns5YsnQXRJRC8Xx/nPMcno=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "0470f36b02ef01d4f43c641bbf07020bcab71bf1",
+        "rev": "e6ab46982debeab9831236869539a507f670a129",
         "type": "github"
       },
       "original": {