I use Photoshop to achieve the halftone effect. If you don't have Ps you could use this website called Photopea. (Essentially a free version of Ps on your browser)
What I do is I duplicate the drawing, select the duplicate and apply the colored halftone effect by going to Filters > Pixelate > Colored Halftone. From here you can experiment with blending modes and the opacity setting. Personally, I always set the blending mode to Soft Light mode and then lower the opacity by 50%. That's how I do it, but feel free to mess around with it, you might find something else you fancy!

Have fun! :)