Use multiple colours to indicate delay severity

Currently, delays are shown in the Trips page - green text is used when departures/arrivals are earlier than expected, and red text is used for delays. However, it would make sense to use a gradient of colours, so that more severe delays are more visually distinguished. For example, On Time Trains (https://www.ontimetrains.co.uk/) uses lime for 1-2, yellow for 3-4, orange for 5-9, and red for 10+ minutes.