You'll notice that your pins will be Pin Drop green. The way to change what your pins look like on the map? Tags.
To change the colour of the pin you have to do this by assigning a tag to your pin. The colour is defined by the first (primary) tag on the pin. If you add more than one tag, you can long press and re-order them on the 'add tag' screen when dropping or editing your pins.
When you create a tag you add a name and then, using the colour wheel, set the colour of the tag. This colour will change the pin colour and how it looks on the map. You can edit this at any time.
To change the pin icon (and colour) on your map, you need to add a customised icon to the tag. To do this, when you edit or create a tag you tap the icon section and can choose from hundreds of icons to visualise on your map.