I have had this Hi-Tec-C multipen for a few months. It is a pink pen body, which is still mostly see through. I originally bought the brown, violet and blue black inks. Recently I added in the clear blue, cherry pink, and apricot orange.
I just did a quick writing sample in a Myndology notebook so you can get a sense of the colors. The brown, blue black and violet inks are fine and what one would expect. The colors are bold and strong. I haven't had many troubles with it not wanting to write which is nice. The .5mm writes much more smoothly than the others.
Out of the three other colors, I find the clear blue to be too much of a sky blue and the orange is difficult to see. The clear blue is the only .5mm refill. The rest are .3mm. I really think that I would be happy if all future refills were .4mm. The blue runs out so quickly but I am okay with that because it gives me a chance to buy more refills.
The cherry pink is nearly a perfect color for me. It isn't red and it isn't pink, but it is a nice color that can pops from the page without trouble. Completely unlike the orange. There isn't much I can do with that color other than doodle.
Notice that the .5mm does look quite a bit larger than the .3mm
On a side note, I absolutely love the Myndology line of notebooks. The paper is nice and responds well to almost all of the pens I have thrown at it so far.