Hi there Phoenix!
Your style of hair is actually much better achieved using a downloaded photo editing software over anything you can use online as the tools they offer are limited and in my opinion... cumbersome.
Despite that... the simplest way using the tools you want to use is to individually make every pixel a different colour. It's a long... arduous... and ultimately boring task.
My advice to you is to download a program called GIMP which stands for GNU Image Manipulation Programme. It's free to download and use and behaves a lot like Photoshop.
In that you could then simply select a segment of pixels, draw a gradient in, flip the selection to the other pixels and either gradient back the other way (like image 2) or colour in with the base colour (more like 1).
I hope that has made some sense to you but feel free to ask me any questions.