I provide two functions.
SetQuiverColor and SetQuiverLength.
The function SetQuiverColor is heavily based on the answer by Suever found on Stackoverflow forum (https://stackoverflow.com/questions/29632430/quiver3-arrow-color-corresponding-to-magnitude).

The function SetQuiverColor allows to change the color of the quiver vectors according to a given colormap.
The function SetQuiverLength allows to have control of the length of the vectors in units of the x/y/z axis.
In addition, SetQuiverLength can take 2 optional parameters:
1) HeadLength: Which allows to manually set the length of the lines constituting the head.
It should be given in units of xyz axis.
2) HeadAngle: Allows to change the angle of the head.
The angle must be given in degrees. The default angle is ~28^\circ

For some yet unknown reasons, the SetQuiverLength requires a pause towards the end of the code. If not there, the values of the vertices are changed only internally and not graphically!
This means that the pause may be too long/too short for your computer and you may have to adjust it sadly... !
If you know a work around, let me know.

An example is given for each function in the header.