This boss has three forms you have to worry about. Playing on easy will, obviously, make things much easier.
The first will have 4 areas you have to attack. Two of each color.
There will be basically a net of fire that you have to be cautious of. Position yourself carefully in front of one of the points you must attack and find where two of the bullet streams of the opposite color cross in front of it. This will let you charge your power attack. Just stay within the streams, carefully as they will move, and continue attacking until the first point is destroyed. You may have to switch colors and drop back to the next crossing of streams.
Once the first is destroyed move over to the next carefully, rinse and repeat. With some cautious movement you should be able to get the hang of this part. Watch for any stray bullets that may come your way, but on easy this shouldn't be much of a problem.
The second part only has two points to attack. It will let out two "snakes" that leave a trail of energy. These will come toward you and wrap around you as you dodge them. If the screen gets too cluttered travel along the trail to absorb it and get it out of your, just be cautious of where they overlap.
Pick one attack point, and move close to it to start. Attack it with the opposite color, the "snake" should wrap around you a bit and you may have to drop back and switch colors, but the first point should go down before it gets too cluttered.
Now focus on taking out the second point and avoiding the trails of energy and you're on to the final part.
This big sphere shaped form isn't really to hard. After the first big attack of white (you can try to use this to boost up your power meter if you go up above the boss, but I wouldn't recommend it if you aren't comfortable, if you're interested try looking up a video on youtube of this boss and you'll see what I mean) He will switch colors and shoot what is basically your power attack at you.
Simply keep your timing with him, and make sure you match his color. His attack will home in on you, if you're the wrong color, obviously, you'll die. If you're the matching color, you will absorb it, and it will instantly fill your meter.
Just keep your timing, switch with him, absorb, then fire it off with the trigger (or whatever button you have your power attack set to) If you time it right, your attack should hit him right after he switches colors for extra damage. Make sure to switch with him so you don't get hit. Just keep changing polarity, firing your attack, switching polarity, firing attack.
You'll get into a groove and you should be good. Just watch for a few stray bullets. I tend to fly in a sort of flight pattern shaped like the symbol for infinity (sideways 8).
After you destroy him, simple dodge the attacks of the final enemy for 60 seconds and you've completed the game.