How I painted the Kraken colour scheme, part of a larger video on painting a variety of Tyranid Hive Fleets.
Start with   Wraithbone .
Wash the whole skin with   Seraphim Sepia .
Pass over all of the skin with thinned   Wraithbone , relayering the skin but leaving some of that wash in the recesses
Highlight up with   Pallid Wych Flesh  Note: For characters, you might want to add a dot highlight of White for extra punch
As a last step, modern versions of Kraken have spots at the top of their limbs and the back of the head, so I painted those on with   Seraphim Sepia . No rhyme or reason to where I put them or how big to make them, just dob 'em on.
Block in all of the carapace, claws and hooves with black, I used   Matt Black 
Glaze toward the back of each plate with   Khorne Red . If you're not confident with glazing, you can either drybrush or relayer entirely with Khorne Red if you'd prefer, the idea is to get a hint of colour under the patterns
Carefully draw on striation lines with   Evil Sunz Scarlet . I pick a spot and draw the lines toward myself when doing this, evenly spacing where I can but not worrying if they're not - It's meant to be biological, and biology is rarely perfect!
Add a second line highlight with   Wild Rider Red  on the striationsNote: For characters and monsters, a point highlight of Fire Dragon Bright right at the edge of the plate where the striations meet will add a bit more punch
Carefully pass over all the splits in the skin and joints with   Thousand Sons Blue . If you overspill, cut back over with your previous colours as necessary. Might get quite messy, but stick with it!
Wash all those areas with   Drakenhof Nightshade .
Relayer any ridges in those splits with   Thousand Sons Blue  and a thin brush.
Add a dot highlights of   Ahriman Blue  for some sheen.
Relayer the whole weapon with   Corvus Black , being careful about overspill (Painting with the gun off the mini is -very- advised)
No need to wash back here, just an edge highlight and choice relayer with   Skavenblight Dinge .
Edge highlight with   Stormvermin Fur .Note: As this goes along side a video tutorial on a wider range of Hive Fleets, I'm using pictures of 'Gants that aren't Behemoth. Colours are all the same though!
Layer over the whole eye with   Averland Sunset 
Relayer again with   Yriel Yellow . It's quite easy to run out of control on these small areas, so take your time. I found that adding a wash into the socket and trying again with Yriel Yellow works well if it goes nuts and I don't catch it in time.
Then coat all the teeth with   Rakarth Flesh 
Wash back with   Agrax Earthshade 
A quick highlight/relayer with   Pallid Wych Flesh , leaving some of that washed Rakarth Flesh near the gum line
  I'm a casual mini painter who's fallen into the tutorial space. Documenting my progress and recipes as I go!