How to make saffron really color my risotto?
How yellow were you expecting it? How much saffron did your recipe call for?

Generally, when a recipe calls for a "pinch" of saffron that can be anywhere from 15-20 stems (expensive, I know). 

Saffron can take time to impart it's yellow coloring, and the depth of that yellow can vary based on the quality, age, or phase of the moon (not really). Some things you can try include:


Soaking the saffron in hot water/stock for 20 minutes to an hour prior to adding.
Grinding the saffron with a mortar/pestle
Using more or a higher quality 


Another thing to keep in mind is that a lot of images aren't purely saffron induced coloring. Often turmeric is used for an additional punch, or even food coloring. Here is an example of an accurate image of a saffron risotto.

Finally, your primary reason for using saffron should be for it's remarkable and unique flavor. The yellow is just a bonus. If you want more than what your batch can give you, well... cheat. :)