Color Ramp in QGIS

In the menu Settings - Style Manager you can see the tag "Color ramp".

By clicking on the green plus you can add manually some color ramps or choose the cpt-city addon the allows you to choose between a lot of different color ramps.

Once you have defined your color-ramp (manually or by cpt-city) you can find it in each style menu (Raster and Vector).

It was not obvious where to look for the predefined templattes, but I figured it out with the help of another question, the credits to this Q&A: Elevation color ramps for DEMs in QGIS

This is mainly about the predefined templattes from the library cpt-city, which has a bunch of nice templattes and is availbale within QGIS.

1. In the Stylepalette of the Layer Properties add a new ramp color as shown below:

2. Then, select the cpt-city option

3. Here you will find the many predefined palettes

Right-click your raster to get the properties dialog of your raster. Select style and set it to single-band pseudo color. On the right-hand side of the dialog there is a set of controls which says "Generate new color map". Click the drop-down to select a pre-existing gradient or scroll down to the bottom of the drop-down to choose 'New color map'.

Here you get a little dialog box where you can make your own or choose from a number of pre-made ones from ColorBrewer or cpt-city. If you want to install a new ramp, search this site and you'll find further instructions (you can also specify them as SVG in another application and import those).