The Absolute Beginners Guide To Amos
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                             Chapter Twenty Four
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We shall now take a look at a few more commands concerning colour.

The COLOUR command seems a bit daunting at first, but like most of the Amos
command set it soon becomes fairly straightforward if you spend a little time
studying it.

When you first load Amos the screen COLOURs are set to default. If you press
escape you will see the infamous yukky brown we all love to hate.
Wouldn't it be nice if we could change them default colours without
resorting to loading a picture or bob bank!  As you can guess it's all
possible in good old Amos. The default screen is a sixteen colour screen.
The COLOUR numbers run from 0 to 15. These 16 numbers are commonly known as
colour indexes. The first colour index (0) is black and the second COLOUR 
index (1) is the horrid brown. If were to enter the following line we could 
change that brown to blue:



COLOUR 1,$00F  ----|
       |           |
       |           |
  Colour index     |
                   |
                   |
               RGB values



The 1 is easy, it's the COLOUR index (or number if you wish) If we wanted to
change the black (COLOUR 0) we would of put 0 instead of 1.

I am going to have explain the second part. The $00F part is commonly known
as an RGB value. You may have come across this in a Paint package such as
Dpaint 3. RGB stands for Red, Green and Blue. You have to assign a value to
each of these primary colours which Amos will then mix for you into a
COLOUR. The range of the values are in a format called Hexadecimal. I am not
going to explain the ins and outs of hex here I will just give you a simple
chart:

  HEX DIGIT    1 2 3 4 5 6 7 8 9 A  B  C  D  E  F

    DECIMAL    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

So from the chart you can see that the maximum value you can use is F (15)
which is the brightest available of the primary colour it is assigned to. 
We assigned $F to B (blue) and 0 to R and 0 to G that works out as :

NO RED    NO GREEN     MAXIMUM BLUE

Example24.Amos is a palette requestor routine written by a clever chap
called Rob Farnsworth. I have included it here as it allows you to see the 
RGB values of colours and anyway it's a superbly written program. 
Load it now!

As seen in Rob's routine you can use the HEX$ instruction to read the COLOUR
assignment of any index:

PRINT HEX$(COLOUR(1))

Would now return our blue (00F) So if we wanted to put back that horrid 
brown, which incidentally is $A40, all we have to do is:

COLOUR 1,$A40

and we are back to normal.

Now we move on to the PALETTE instruction which is really just a more
powerful version of COLOUR. PALETTE allows you to set as many COLOUR
commands as you want in one statement. Very handy if you want to change a lot
of colours in one go:

PALETTE $FFF,$00F

Would change COLOURs zero and one. PALETTE is quite flexible, you can insert
a comma (,) to skip any COLOUR you do not want to change so if for example
we wanted to change COLOURs 0,1 and 6 we would do  this:

PALETTE $FFF,$00F,,,$0F0,,,,,,,,,
          |       |   |
          |       |   |
       COLOUR 0   | COLOUR 6,NOW GREEN    
       NOW WHITE  |
                  |
               COLOUR 4
            STAYS AS IT WAS
       AS DO 3 & 5 & 7 ONWARD 
  
To save confusing you I have been putting leading zeros in the RGB values. 
If you put $000 in your Amos listing it will be changed to just $0 for you 
so don't worry if this happens.  Now load Example24.Amos.
 
                              End of Chapter 24
                              ^^^^^^^^^^^^^^^^^