some of the colors names dont match with the posca website names for example khaki green only shows up on the 3m range not the 5m range. why?

There's two answers here, but the answer is because this set for sale is the Japanese set. They 1) have different names for some of their colors and 2) they have other colors available from the western distributor of posca pens. Here's some of the differences explained: Differing names: PC-5M-3 - Bright Yellow / Yamabuki / Orangy Yell.ow PC-5M-5 - Light Green / Yellow Green PC-5M-12 - Purple / Violet PC-5M-13 - Pink / Peach / Momo PC-5M-37 - Gray / Ash PC-5M-P11 - Lavender / Pastel Purple PC-5M-P2 - Sunshine Yellow / Pastel Yellow PC-5M-P4 - Apricot / Pastel Orange PC-5M-P6 - Aqua Green / Pastel Green Colors only in Japanese line for PC-5M: PC-5M - 7 - Khaki Green PC-5M - 9 - Navy Blue PC-5M - 14 - Dark Red PC-5M - 22 - Dark Brown (Note: These colors are available in western line for PC-3M though, which are not available in Japanese PC-3M line) The rest of the colors you've seen on the western color guide pamphlet are only available as the western version of the pens and are not included in this set, including but not limited to: Prussian Blue, Ochre, Emerald Green, Lilac, Beige, Ivory, Ruby Red, Raspberry, Red Wine, Slate Gray, Apple Green, Straw Yellow, English Green, Cacao Brown, Deep Gray, Bronze, Metallic Red, Metallic Pink, Metallic Violet, Metallic Blue, Metallic Green, Fluorescent Yellow, Fluorescent Orange, Fluorescent Red, and Fluorescent Pink. At least for now, until this set or those options change.

The official Posca website states that there are 42 colors in the full 5m set. Which 13 are missing from this one?

This is the full range for the Japanese Line of the PC-5M. The western distributor seems to have other colors available according to their online color guide. They seem to be the same pens, though of course these have Japanese writing, and some of the colors are named differently in Japanese (EG "momo", translated to "peach" in the description, corresponds to the "pink" color - PC-5M-13). The colors included in this set are: White, Yellow, Bright Yellow, Orange, Yellow Green (Light Green), Green, Khaki Green (not available in 5M in western line, khaki only comes in 3M), Light Blue, Navy Blue (also not available in 5M in western line), Fuscia, Purple (Violet), Peach (Pink), Dark Red (Also not available in 5M in western line), Red, Brown, Dark Brown (also not available in 5M in western line), Black, Blue, Ash (Gray), Sky Blue, Light Pink, Light Orange, Coral Pink, Pastel Purple (Lavender), Pastel Yellow (Sunshine Yellow), Pastel Orange (Apricot), Pastel Green (Aqua Green), Silver & Gold. The other PC-5M colors listed on the western distributor's color guide that are NOT included in this set are: Prussian Blue, Ochre, Emerald Green, Lilac, Beige, Ivory, Ruby Red, Raspberry, Red Wine, Slate Gray, Apple Green, Straw Yellow, English Green, Cacao Brown, Deep Gray, Bronze, Metallic Red, Metallic Pink, Metallic Violet, Metallic Blue, Metallic Green, Fluorescent Yellow, Fluorescent Orange, Fluorescent Red, and Fluorescent Pink. This all assumes of course that 1) you receive the correct pens and 2) this set and information are not changed up in future.

Can anyone help me understand why I would use these instead of just some paint a a paint brush?

From what I personally have learned is this-people who are already artistic do well with paint brushes! They have the artist hand to do so...they also use paint pens & paint and brush...I have tried to do paint and brush but I can hardly draw stick figures so I was not good at it, but I admit I didn't practice. I can use paint markers better, not great but better. I hope this helps :)

Manufacturer	Uni Posca
Brand	Unifilter
Model Number	PC5M29C
Colour	Multicolor
Closure	Pull Cap
Material	(Plastic; Pigment; Water; Acrylic; Fiber Nib)
Number of Items	1
Size	29 count (Pack of 1)
Point Type	Medium
Line Size	1.8-2.5 Millimeters
Ink Colour	Blue,White,Gold,Pink,Silver,Black
Tip Type	metal
Manufacturer Part Number	PC5M29C
Manufacturer	Uni Posca

Uni Posca Full Acrylic Paint Pens with Reversible Medium Point Pen Tips, Posca Pens are Acrylic Paint Markers for Rock Painting, Fabric, Glass Paint, Metal Paint, and Graffiti - Set of 29, Multicolor

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