You didn't indicate what model you are using but it could be several things.
If your coffee isn't ground fine enough your brewing time may be too short. Your double espresso shot should take between 18-26 seconds to brew. A single should take between 9-13 seconds to brew.
If you are getting the correct brew time, try a different coffee bean. Some coffee is roasted more that others and that could be the reason the color is light. Make sure you are using fresh beans too.
Make sure you are putting the correct amount of ground coffee into the porto filter and tamping it well. A porto filter that isn't full will not brew a good shot.
Answers & Comments
You didn't indicate what model you are using but it could be several things.
If your coffee isn't ground fine enough your brewing time may be too short. Your double espresso shot should take between 18-26 seconds to brew. A single should take between 9-13 seconds to brew.
If you are getting the correct brew time, try a different coffee bean. Some coffee is roasted more that others and that could be the reason the color is light. Make sure you are using fresh beans too.
Make sure you are putting the correct amount of ground coffee into the porto filter and tamping it well. A porto filter that isn't full will not brew a good shot.