A method to get colorblind friendly version of Fork.app

recolor-fork.sh

#!/usr/bin/env bash
set -euo pipefail

# === CONFIGURATION ===
APP_SRC="/Applications/Fork.app"
APP_DEST="./Fork.app"
DYLIB_NAME="ColorTap.dylib"
COLOR_SRC="ColorTap.m"
INSERT_REPO="https://github.com/Tyilo/insert_dylib.git"

# === STEP 0: Fresh copy of Fork ===
echo "→ Copying Fork.app locally..."
rm -rf "$APP_DEST"
cp -R "$APP_SRC" .

# === STEP 1: Create ColorTap.m if missing ===
if [[ ! -f "$COLOR_SRC" ]]; then
  cat >"$COLOR_SRC" <<'EOF'
// ColorTap.m — minimal Fork diff recolor
#import <Cocoa/Cocoa.h>
#import <objc/runtime.h>
static inline NSColor *RGB(int r,int g,int b,CGFloat a){
  return [NSColor colorWithSRGBRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:a];
}
static inline NSColor *RemovedLine(){return RGB(101,72,60,1);}
static inline NSColor *RemovedWord(){return RGB(174,95,52,1);}
static inline NSColor *AddedLine(){return RGB(39,69,111,1);}
static inline NSColor *AddedWord(){return RGB(39,85,149,1);}
static NSColor *OverrideForName(NSString *n){
  if(!n)return nil;
  static NSDictionary *m; static dispatch_once_t once;
  dispatch_once(&once,^{
    m=@{
      @"diffaddedcolor":AddedLine(),
      @"diffremovedcolor":RemovedLine(),
      @"diffaddedhighlightbackgroundcolor":AddedWord(),
      @"diffremovedhighlightbackgroundcolor":RemovedWord(),
      @"mergeaddedbackgroundcolor":AddedLine(),
      @"mergeremovedbackgroundcolor":RemovedLine(),
      @"mergelocalbackgroundcolor":AddedLine(),
      @"mergeremotebackgroundcolor":RemovedLine(),
      @"mergeunmergedbackgroundcolor":AddedLine(),
    };
  });
  return m[n.lowercaseString];
}
@interface NSColor(Tap)
+ (NSColor*)tap_colorNamed:(NSColorName)n;
+ (NSColor*)tap_colorNamed:(NSColorName)n bundle:(NSBundle*)b;
@end
@implementation NSColor(Tap)
+ (NSColor*)tap_colorNamed:(NSColorName)n{
  NSColor*o=OverrideForName((NSString*)n);
  return o?o:[self tap_colorNamed:n];
}
+ (NSColor*)tap_colorNamed:(NSColorName)n bundle:(NSBundle*)b{
  NSColor*o=OverrideForName((NSString*)n);
  return o?o:[self tap_colorNamed:n bundle:b];
}
@end
__attribute__((constructor))
static void tap_init(void){
  Class c=object_getClass([NSColor class]);
  struct{SEL a;SEL b;}p[]={{@selector(colorNamed:),@selector(tap_colorNamed:)},
                           {@selector(colorNamed:bundle:),@selector(tap_colorNamed:bundle:)}};
  for(int i=0;i<2;i++){Method A=class_getClassMethod(c,p[i].a);
    Method B=class_getClassMethod(c,p[i].b);
    if(A&&B)method_exchangeImplementations(A,B);}
}
EOF
fi

# === STEP 2: Build dylib ===
echo "→ Building $DYLIB_NAME..."
SDK=$(xcrun --sdk macosx --show-sdk-path)
clang -arch arm64 -dynamiclib -fobjc-arc -isysroot "$SDK" -framework Cocoa \
  -o "./$DYLIB_NAME" "./$COLOR_SRC"
codesign -f -s - "./$DYLIB_NAME"

# === STEP 3: Place dylib inside app ===
echo "→ Inserting into Fork.app..."
mkdir -p "$APP_DEST/Contents/Frameworks"
cp -f "./$DYLIB_NAME" "$APP_DEST/Contents/Frameworks/$DYLIB_NAME"

# === STEP 4: Build insert_dylib if missing ===
if [[ ! -x ./insert_dylib/insert_dylib ]]; then
  echo "→ Building insert_dylib..."
  rm -rf insert_dylib
  git clone --depth=1 "$INSERT_REPO" insert_dylib
  xcodebuild -project insert_dylib/insert_dylib.xcodeproj -scheme insert_dylib \
    -configuration Release -arch arm64 build >/dev/null
fi

INS=$(find ~/Library/Developer/Xcode/DerivedData -type f -path "*/Release/insert_dylib" -perm +111 2>/dev/null | head -n1)
[[ -x "$INS" ]] || INS="./insert_dylib/insert_dylib"

# === STEP 5: Patch Fork binary ===
echo "→ Patching binary..."
"$INS" --inplace --strip-codesig \
  @executable_path/../Frameworks/$DYLIB_NAME \
  "$APP_DEST/Contents/MacOS/Fork"

# === STEP 6: Re-sign everything ad-hoc ===
echo "→ Re-signing..."
codesign -f -s - "$APP_DEST/Contents/Frameworks/$DYLIB_NAME"
codesign -f -s - "$APP_DEST/Contents/MacOS/Fork"
codesign -f -s - --deep "$APP_DEST"

# === STEP 7: Verify and launch ===
echo "→ Verifying patch..."
otool -L "$APP_DEST/Contents/MacOS/Fork" | grep "$DYLIB_NAME" || echo "⚠️ Missing link!"
echo "→ Launching Fork..."
open "$APP_DEST"

Instructions:

mkdir colorblind
cd colorblind
curl -O https://gist.githubusercontent.com/NinoScript/2dfb983de3bf5620beb8304ce653e05c/raw/c80548c7077ce0245169657ab502dee67eecf026/recolor-fork.sh
chmod +x recolor-fork.sh
./recolor-fork.sh

Note: Always be cautious when running code you find online.

Using these colors replicates the default Fork behavior:

static inline NSColor *RemovedLine(){return RGB(99,63,62,1);}
static inline NSColor *RemovedWord(){return RGB(159,67,71,1);}
static inline NSColor *AddedLine(){return RGB(58,92,63,1);}
static inline NSColor *AddedWord(){return RGB(56,132,66,1);}

These replicate GitHub's colorblind theme:

static inline NSColor *RemovedLine(){return RGB(44,31,26,1);}
static inline NSColor *RemovedWord(){return RGB(114,62,34,1);}
static inline NSColor *AddedLine(){return RGB(20,35,56,1);}
static inline NSColor *AddedWord(){return RGB(35,77,135,1);}

But I found that GitHub's darker colors do not work so well with the lighter background.
So in the script I used these values to have about the same brightness as Fork's colors, but the same hues as GitHub's colors.

static inline NSColor *RemovedLine(){return RGB(101,72,60,1);}
static inline NSColor *RemovedWord(){return RGB(174,95,52,1);}
static inline NSColor *AddedLine(){return RGB(39,69,111,1);}
static inline NSColor *AddedWord(){return RGB(39,85,149,1);}