---
title: "How to add a cool tone filter with Claude (tested prompt and ffmpeg command)"
description: "At one second the shot slides into an icy blue-cyan cast in half a second, the warm rainbow flecks in the backdrop turning cold blue while the brightness stays the same. Install one skill and ask Claude Code, or run the ffmpeg command we tested yourself."
url: https://www.recharm.com/effects/cool-tone-filter
---

# How to add a cool tone filter with Claude

At one second the shot slides into an icy blue-cyan cast in half a second, the warm rainbow flecks in the backdrop turning cold blue while the brightness stays the same.

Made by the command on this page, from our own test clip.

## Get this effect

1. ### Switch to Code in your [Claude Desktop App](https://claude.com/download)

2. ### Install the skill (once)

   ```
   Install the Recharm video effects skill: download https://recharm-growth-staging.s3.us-east-2.amazonaws.com/website/downloads/recharm-video-effects.zip and unzip it into ~/.claude/skills
   ```

3. ### Ask for the effect

   ```
   Add a cool tone filter to input.mp4
   Second the cool tone starts: 1.0
   Seconds the shift from the original colors takes: 0.5
   ```

## Several videos, several effects, one ask

Put your clips in the folder, mention them with @, and ask for everything at once. Claude runs one tested script after another on each clip, then joins them.

Add a cool tone filter to **@clip1.mp4**, put a sale badge on **@clip2.mp4**, give **@clip3.mp4** a VHS look, then join all three with crossfades.

## Settings you can change

Ask Claude to change any of these, or edit them at the top of the command.

| Setting | Default | What it does                                                                                 |
| ------- | ------- | -------------------------------------------------------------------------------------------- |
| `START` | `1.0`   | Second the cool tone starts. 0 cools the clip from the first frame.                          |
| `FADE`  | `0.5`   | Seconds the shift from the original colors takes.                                            |
| `COOL`  | `0.15`  | How cold the tone is: red taken out and blue added at every brightness level. 0.3 looks icy. |

## Without the skill

Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the command itself.

```
Give input.mp4 a cool blue-cyan tone. Leave the first 1.0 second untouched, then over 1.0 to 1.5 seconds blend smoothly into the cool grade and keep it to the end. The cool grade: ffmpeg colorbalance with red -0.15 and blue +0.15 in the shadows, mid-tones and highlights (rs=-0.15:bs=0.15:rm=-0.15:bm=0.15:rh=-0.15:bh=0.15) and preserve lightness on (pl=1), so the frame keeps its brightness (within about 5% of the original) while blue becomes clearly the strongest channel and red the weakest (around RGB 160, 190, 228 on average for a bright frame). Add no text (any text you do add should be drawn with Pillow, not ffmpeg's drawtext). Keep the size, the 30fps frame rate, the 6 second length and the audio. Use ffmpeg and save it as output.mp4.
```

## Run it without Claude

This is the exact command we tested. Save it as `cool-tone-filter.sh` and run:

```
sh cool-tone-filter.sh input.mp4 output.mp4
```

```
#!/bin/sh
# Cool tone filter: from 1s the whole picture slides toward icy blue-cyan over half a second, at the same brightness.
# Usage: sh cool-tone-filter.sh input.mp4 output.mp4
set -e
IN="$1"; OUT="$2"
START=1.0   # second the cool tone starts; 0 cools the clip from the first frame
FADE=0.5    # seconds the shift from the original colors takes
COOL=0.15   # how cold: red taken out and blue added in shadows, mid-tones and highlights (0.3 is icy)

# The cool grade: less red, more blue at every brightness level, luminance preserved so nothing gets darker
GRADE="colorbalance=rs=-$COOL:bs=$COOL:rm=-$COOL:bm=$COOL:rh=-$COOL:bh=$COOL:pl=1"
# Blend from the untouched shot to the graded one as the clock passes START
ffmpeg -y -i "$IN" -filter_complex "\
[0:v]format=gbrp,split[orig][c];\
[c]$GRADE[cool];\
[orig][cool]blend=all_expr='A+(B-A)*clip((T-$START)/$FADE,0,1)',fps=30,format=yuv420p[v]" \
  -map "[v]" -map 0:a -c:v libx264 -crf 18 -pix_fmt yuv420p -c:a copy "$OUT"
```

## More color looks

- [Apply a LUT **Apply a LUT**](https://www.recharm.com/effects/apply-a-lut)
- [Black and white **Black and white**](https://www.recharm.com/effects/black-and-white)
- [Bleach bypass **Bleach bypass**](https://www.recharm.com/effects/bleach-bypass)
- [Cinematic color grade **Cinematic color grade**](https://www.recharm.com/effects/cinematic-color-grade)
- [Color match **Color match**](https://www.recharm.com/effects/color-match)

## Find 3x _winning ads_

Recharm cuts your ad footage into tagged, searchable clips: hooks, testimonials, product shots. Find the shots that win, add the effect with Claude, and ship 3x more ad edits.

[Start 14-day free trial](https://www.recharm.com/get-started)