Hi Keith,

> Le 28 avr. 2022 à 06:05, Keith McKay via ntg-context <ntg-context@ntg.nl> a écrit :
> 
> Hi,
> 
> In the MWE below I define an rgb colour, myColor1, using random numbers for the r, g and b components. I then use it to fill a unitsquare the size of the page, which works as expected. In the loop that follows I then use the defined colour, myColor1, along with white and the variable r to create shades of myColor1 as in the MWE below. However, myColor1 is not recognised in the loop and seems to be replaced by black, although if I use a predefined colour, in this case BurntSienna from the crayola collection, it works as expected.  I have tried a number of ways to get this to work as shown in the code but without success. I would be grateful for any suggestions.
> 
> Best Wishes
> 
> Keith McKay
> 
> %%%%%%%%%%%%%%%%%%%%MWE%%%%%%%%%%%%%
> \setuppapersize[A4,portrait]
> \usecolors[crayola]
> \starttext
> \dorecurse{10}{
> \startMPpage
> StartPage;
> \definecolor[name="myColor1", r =  uniformdeviate(1), g = uniformdeviate(1), b = uniformdeviate(1) ] ;
> fill unitsquare xscaled PaperWidth yscaled PaperHeight withcolor  "myColor1";
> for i =2 step 2 until 10:
> r := i/10;
> fill unitsquare xscaled 5cm yscaled .5cm shifted (1cm,i*cm) withcolor(r[\MPcolor{BurntSienna},white]);
> fill unitsquare xscaled 5cm yscaled .5cm shifted (7cm,i*cm) withcolor(r[\MPcolor{myColor1}, white]);
> fill unitsquare xscaled 5cm yscaled .5cm shifted (13cm,i*cm) withcolor(r[\MPcolor{"myColor1"}, white]);
> %fill unitsquare xscaled 5cm yscaled .5cm shifted (13cm,i*cm) withcolor(r[myColor1 ,  white]); This line causes an error.
> endfor;
> StopPage;
> \stopMPpage
> }
> 
> \stoptext
> %%%%%%%%%%%%%%%%%%%%%%%%%%%end MWE%%%%%%%%%%%
> 

Here is a solution, with works here, defining in another way the color «  myColor »:

\setuppapersize[A4,portrait]
\usecolors[crayola]
\starttext
\dorecurse{2}{
\startMPpage
StartPage;
color myColor ;
myColor := (uniformdeviate(1),uniformdeviate(1),uniformdeviate(1));
fill unitsquare xscaled PaperWidth yscaled PaperHeight withcolor myColor;
for i =2 step 2 until 10:
r := i/10;
fill unitsquare xscaled 5cm yscaled .5cm shifted (1cm,i*cm) withcolor(r[\MPcolor{BurntSienna},white]);
fill unitsquare xscaled 5cm yscaled .5cm shifted (7cm,i*cm) withcolor(r[\MPcolor{myColor1}, white]);
fill unitsquare xscaled 5cm yscaled .5cm shifted (13cm,i*cm) withcolor(r[\MPcolor{"myColor1"}, white]);
%fill unitsquare xscaled 5cm yscaled .5cm shifted (13cm,i*cm) withcolor(r[myColor1 ,  white]); This line causes an error.
endfor;
StopPage;
\stopMPpage
}

\stoptext

Fabrice.
> 
>     
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