Question: setting graph colours

I want to plot a bunch of straight lines with positive slope in one colour, and I want to plot a single line of negative slope in another colour.

I hope my code is self-explanatory:

restart; with (plots):
for i from 1 to 5 do;
 [y - x = 1, y - x = 2, y - x = 3, y - x = 4, y - x = 5]
implicitplot([op(myEqns), y+x=0], x=-10..10, y=-10..10, colour=[red,blue]); 

# the last line appends the line with negative slope (y+x=0) to the list of lines with positive
# slope.

My problem is that MAPLE makes the lines *alternate* between red and blue, whereas I want *all* my positive-slope lines in red and *only* my negative-slope line in blue.

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