Jaguar:Video Output Notes

RGB
The Atari Jaguar will output RGB natively and only an RGB cable is needed. You can make one yourself, but some sellers are listed below.

Sellers

 * Atari Jaguar RGB SCART cable (US Seller)

Video Port Pinout
The cable plug uses a 24-pin dual-edge connector (.100 DIP).

When making an RGB cable:
 * Wire RGB to pins 4B, 7A, 5A (respectively).
 * Wire RGB ground to pin 10B.
 * Wire CSYNC to pin 5B with a 680 ohm, 1/4 watt resistor and a 220uF/16v capacitor in series.
 * Make sure to not share video ground with audio ground. Audio ground will be tied to pin 2A.

Here's a diagram from Atarimax.com: