Dozy;
As a refresher, the altimeter scale is displayed in white, the digital numbers in green, all against a gray background.
The analog vertical speed needle is green and the scale is white on a gray background. The digital display normally "attaches" itself to the analog needle as shown by the first image.
As shown in the 2nd image, at vertical speeds greater than 6000fpm the analog needle stays at the end of the scale and it is both the digital display and analog needle which turn amber. The digital rate of descent is displayed at the bottom or top of the VS display as appropriate.
In our sim exercise (A330) the analog standby altimeter needle was going around the dial once every 3 seconds...THAT gets one's attention.