Magenda and White colors are gradients, but other colors show as solids work

check your voltage begin and end of the ledstrip, for ledstrips and PI can be slightly more also than 5.0 volts.

If you have that PSU used together for PI AND ledstrip simultaneously: crank it up until 5.3 volts and power the ledstrip from both sides.

so

GND begin and end connect together

+5volts begin and end together.

make sure you have a good GND over at least 2 PINS GND going to PSU and ledstrip's GND