Open almost any panchang app and Rahu Kaal is the loudest thing on the screen: a red bar, sometimes a warning icon, often a countdown. Chakra shows the same window in a quiet grey. That is a deliberate choice, and it comes from what Rahu Kaal is.
Rahu is a shadow
Rahu and Ketu are not bodies you can point a telescope at. They are the two points where the Moon's orbit crosses the plane of the Sun's apparent path — the lunar nodes. Classical texts call Rahu chhaya, shadow. Eclipses happen near these points, which is why the old stories describe Rahu swallowing the Sun or Moon.
Because Rahu is a shadow-point rather than a light, the tradition treats its hours as a time to hold off on starting something new, not as a time when harm arrives. It is closer to "wait for a better slot" than to "danger". A red bar overstates it. Grey is the honest colour, and it is the one the tradition itself uses for chhaya.
How the window is built
Rahu Kaal is a fixed fraction of the daylight, not a clock hour. Take the time from sunrise to sunset and divide it into eight equal parts. One of those parts belongs to Rahu, and which one depends on the weekday. Sunday's falls late in the afternoon; Monday's comes soon after sunrise; the other days sit in between. Yamaganda and Gulika Kaal are built the same way, from other eighths.
Two things follow from that. First, Rahu Kaal is longer in summer and shorter in winter, because the daylight it divides is longer or shorter. Second, it starts and ends at a different clock time in every city, because sunrise and sunset do. A panchang that prints "Rahu Kaal 4:30–6:00 PM" as a fixed national figure is rounding away the part that depends on where you are.
Chakra computes the window from your city's own sunrise and sunset for the day you are looking at. You can see it on any daily panchang page and on today's panchang, drawn on the same timeline as the auspicious windows so you can read the whole day at once.
What to do with it
If you keep Rahu Kaal, the usual practice is simple: avoid beginning a journey, a purchase, or a ceremony during it, and carry on with anything already under way. Routine work, travel you cannot reschedule, and daily prayer are not affected.
If you do not keep it, nothing about the rest of the panchang changes. The tithi, the nakshatra, the sunrise and the festival dates are all computed the same way regardless. Rahu Kaal is one window among several, shown for the people who use it, in a colour that matches what it is.
The method behind every timing on the site is written up on the methodology page.