Those fiber optic backlight panels are a bit tricky. I tested them with different configurations (that's why stuff is connected in the pics so poorly):

The fibers have to be positioned to point straight to the LED to get enough light out of them. There has to be also some diffuser film between to get uniform color across the panel. Otherwise some fibers may have different color than others.

In a dark or shady room the cover is almost too bright. Normal house lightning is ok too, but the the effect is not so notable. Note that I haven't tested 5 V yet, only 3,3 V.

At sunlight there should be a wall of superbright leds to see changes in illumination, two leds just doesn't cut it. Adding more leds is not an option, because they draw too much power. Those 2 RGB leds will draw about 120 mA (60+60) at full brightness which will significantly reduce battery duration.