Learning Sudoku without any numbers

I really enjoy Sudoku puzzles, but I've found a lot of people are turned off by all the numbers.
They make the understandable mistake of assuming the numbers need to be added or subtracted, or manipulated in some way, which sounds a lot like maths, which they probably learned to hate at school.

I've put together this guide to show how Sudoku is actually a really fun logic puzzle, which has nothing to do with maths.

Please enjoy, and share with anyone you know who enjoys puzzles, but never looked twice at Sudoku.

The aim of Sudoku is to fill the entire grid, knowing that each colour appears once, and only once, in each column, in each row, and in each of the 9 squares.
If a square has a purple in it, the other spots in that square can't be purple.
If a row has all the colours except blue, then the remaining colour has to be blue.
We use the colours we have to slowly fill more spots, each of which can be a clue to fill yet another spot.

The centre square needs a black, and the two black bordered rows each have one, leaving only one place the black can go, so we'll add it in.

The square to the left needs a light-green. Again, we have two rows which already contain light-green, so we know the light-green for this square belongs in the middle row, next to the red, but on which side? Happily, there's a light-green in the far left column, leaving only only place the light-green can go.

We can follow the same process to add a red, a blue and a mustard. Watch the gif until you understand what's going on, because we're going to change it up a bit next.

This row full of question marks needs a purple, and our previous efforts have almost filled the square to the left. That square can only have one purple, so that row's purple has to be in the only other empty spot, over on the right.
I've jumped ahead and filled in some more of the puzzle, using the same methods; but they can only take us so far.

The top left square is empty, so there's not much scope for using our previous techniques.
We got lucky though. Mustard, light-green, black, grey and blue all appear in this column, and red, navy and purple already appear in the intersecting row. Using any of these colours would mean having that colour appear twice in either that row or that column. The only remaining colour is green, so let's add it.

While the square is almost empty, that column is starting to fill up, which gives us some options. There's only one place that column's red can go, which then leaves only one place for the purple.
Simple elimination then gives us the navy, as its the only colour missing from that column.

We've made a lot of progress. Pause for a while and see if you can spot any other opportunities. To be honest, I was stuck here for a few hours, so don't feel bad. Any green possibilities, perhaps?

The marked row is missing green, navy and purple. The centre square already contains green and navy, so we can put in the purple.

Did you spot the green I mentioned? Adding this offers some interesting possibilities, since we now have a column with 3 colours missing, which is part of a square with 6 colours missing.

That column needs navy, grey and black, so mustard light-green and blue belong in the middle.
This lets us rule out blue and light-green for the centre spot, leaving mustard as the winner.

I'm speeding things up a bit by including more in each gif.
Don't be concerned if you miss one, just wait til it comes around again. A single question mark signifies that either that row, column or square only has that colour missing.

Ignore the strange lines outside the grids. I pasted from excel into paintbrush and ended up copying over some unrelated borders. I didn't notice til I'd made the gifs.

I used http://gifcreator.me/ An excellent, free tool.

There are only a few empty spots now, all of which can be easily filled.
I won't though, because I like trolling people.

You can see now, how its easier and simpler to use numbers, since they're a lot easier to fill in with a single colour pen. We could use widgets like smiley face, moon, sun, flower etc, but its a lot simpler to mentally run through a series of numbers and note which ones are missing.

Here's the well worn original I used.

Have fun