Hello there! Welcome. Based on your post I'm assuming you are new to the hobby and hopefully I can give you some tips.
I just grab the SC box about a month ago, but I have been playing Warhammer 40k for about 3 years now.
First off, I'm assuming since you've glued everything together that you got all the good hobby tools: snippers, mould line remover, files, exacto knife, and glues (super or plastic). Make sure you clean up your mould lines (the lines that are usually where two halves of the plastic mould meet) by using an exacto knife or the mould remover tool. These stand out dramatically once paint is applied and really distracts from the overall feel of the model. Also, clean up any pieces of sprue that are still attached to your model, and file off the excess.
Once your model is "cleaned up", you can either choose to go ahead and glue it to the provided bases (the black circles or squares that came with your box) or do the base separate (that's a different topic we can delve into later if you want). Time to prime! I use the expensive overcosted Games Workshop Citadel Chaos Black primer because its very smooth. You can pick up any type of plastic primer from a hardware store though and save some money. Make sure you spray roughly an arm's length away from the model and do bursts of spray instead of heavy coats. This helps maintain the detail on the model. Let it dry for at least 15 minutes (I usually do a bunch at once then come back later in the day).
Next, its time for paints! If you stick with Citadel paints (there's also P3, Vallejo, ie) then there are different types of paint, which usually means different saturation of pigment). You have your
base paints, which are higher pigment concentration, these go on first to provide a good foundation for the rest of your paint layers. Always thin down your paints with a
little bit of water to make it smooth. 2 thin layers is always better than 1 thick layer, don't clog those details! Next are your
layer paints, these go over your base paints and have a little less pigment in them, so the base color adds to your layer paint. Once both of these types are down, its time for a good
wash. These are extremely watered or diluted down paints that are the consistency of water. These are used to pull out the details of your model. You want to use a good amount of this, but make sure it doesn't pool in any section. Let this dry for AT LEAST an hour. Once that's done, its time to use some different, preferably more bright layer paints - this is called
highlighting. You want your highlights to be close to the same color family as your layer paints as you are just really brightening up the model again since the wash darkened the model down. If this is your first time painting, I wouldn't worry about edge highlighting as much, its something I still don't do as I don't have the patience.
There is also a great technique for scales and us Seraphon players called
drybrushing. This is SUPER easy. Basically you want to get a drybrushing brush as the bristles are much different. Dab a little paint onto it, and then user a paper towel to wipe most of it off, then you will just "paint" the model lightly and the paint will catch the details and edges. GW does make a separate Drybrush style of paint? They are thick, kind of like PlayDough, I've only used a couple, they are OK.
A good rule of thumb for table top is 3 colors. Now its time for hopefully answering your question about the color scheme!
For what you are wanting (red skin, yellow scales), this is what I would advise:
Scales
Instead of yellow (yellow pigment is a pain to paint, at least for me) I would do a tan/brown, which would match closer to the "Desert Sand" feel.
Base:
Zandri Dust
Wash/Shade:
Agrax Earthshade
Layer (drybrush):
Ushabti Bone
Skin
Base: Darker Red:
Khorne Red or a bit brighter
Mephiston Red
Wash/Shade: Use the Agrax again to save money, this will make it look more "muddy", or
Nuln Oil to make it look a bit darker, and not as... muddy? Just dark.
Layer (drybrush OR highlights):
Evil Sunz Scarlet or highlights with
Wild Rider Red (this is very bright)
Leather straps and bits can be: Dryad Bark or Rhinox Hide, then use Gorthor brown for highlights.
Gold icons and bits can be: Balthasar Gold then one of the Gold layer paints (I use Gehenna's Gold).
I hope this helps!
