Hi Wolfgang,

Thank you for your reply. I did as you suggested but it still never worked. However it did make me delve further into the Metafun, LuaMetaFun and the Colouring ConTeXt manuals where I found examples of the resolvedcolor helper which I used as follows:

definecolor [name = "myColor", r = uniformdeviate(1), g = uniformdeviate(1), b = uniformdeviate(1)];

for loop..

fill unitsquare xscaled 5cm yscaled .5cm shifted (7cm,i*cm) withcolor(r[resolvedcolor("myColor"), white]);

endfor;

I also found the namedcolor helper and I could use it as follows:

fill unitsquare xscaled 5cm yscaled .5cm shifted (1cm,(2*i)*cm) withcolor namedcolor("myColor2") ;

However, for some reason it did not work in:

fill unitsquare xscaled 5cm yscaled .5cm shifted (7cm,i*cm) withcolor(r[namedcolor("myColor"), white]);

Thanks again for your suggestion

Best Wishes

Keith

Keith McKay via ntg-context schrieb am 28.04.2022 um 12:05:

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) ] ;

Remove the backslash in front of the definecolor command.

Wolfgang