How do I do this? - Any Help much appreciated

Questons like this are hard to answer without knowing your experience level with AE and other graphics programs like Photoshop and Illustrator.

The first thing to consider would be what type of graphic is this? Is it a flat JPEG or PNG? Is it a layered file like an AI or PSD?

AE works by animating layer, their properties (position, scale, etc.) and Effects (gaussian blur, fill, etc.).

So the simplest way to start with something like this is to have a layered Illustrator file where each of the graphics including the text is a separate layer.

If you don't have a layered file you can use a flat file in AE: duplicate the layer five times and use a mask to cut out the arrows and center circle so each is isolated onto it's own layer.

I would have two different layers for each arrow a dm one and a color one.

The dimming would be accomplished by animating the opacity of the dim layer arrows.

The color animation you described could be created using the radial wipe effect (Effect > Transition > Radial Wipe) on the colored arrow layer. This effect makes a layer appear/vanish in a circular direction.

In general that is the approach I would take. 

But all sorts of problems/opportunities arise when working on an animation.