Lordroy, first I must correct myself. Vellejo does not make a "Heavy Yellow". The color I was thinking of is Vellejo's "Heavy Goldbrown #72151" which looks like a heavy yellow, somewhere between yellow & brown. It is like all of Vellejo's Heavy Opaques, a very good base color to start off with.
Now, back to the question. Andrea's Yellow Paint set is a set of six yellow paints that go from a very light yellow and progress toward a much darker yellow. They are indeed paints and not a primer among them so you can use them as you described but it's true value lies in the way you can blend them into a very silky smooth transition with great ease. If you choose, you can go with the directions that come with the set, which is to start with the third or fourth shade as the base so you'll have either two lighter shades & three darker ones or vice versa. For me, if I have to paint something like a GW Imperial Fist Space Marine, I can just pull out this set of paints and without a great deal of mixing, paint it up with some fantastic results. Now, it's fast and easy to use but you can still do the same quality work by mixing your own shades of paint with other brands like Reaper or the Vellejo Model Color set. I have both compleat sets and have done so with each. However, Andrea's Paint Sets make it much faster and easier. Some colors are difficult to mix for newer painters. Take reds for instance. If you have a mini with a cloak you want to paint red, well you can base it with whichever shade of red you like but you can't just add white to it because it'll just turn it pink! To lighten a red you would need to add a tiny bit of yellow (three parts red w/one part yellow) or better yet a bit of orange (two parts red w/one part orange). You would then add your diluant/thinner & flow improver to the mix and continue the prosses until you have the results your looking for. This can take quite a bit of time and paint which can get expensive! For me, it's much faster and in the long run, cheaper to use Andrea's Red Paint set. I would recommend to any painter to buy a Pocket Color Wheel and the "color mixing bible" by Ian Sidaway. These two items are a godsend to me. I hope I wasn't too verbose and I hope I helped you.
Keep painting & Stay Frosty!
