How to color vector as defined value and defined colors

Hi all,

I have plotted a figure using "gsn_csm_vector_scalar_map_ce(wks, u,
v, var1)" (see attached figure). Now I want to color the vectors by
another scalar variable, say var2.

Var2 is the degree of the vector: if the vectors point up, then
define the degree is 0. If the vectors point left, define -90. If the
vector point right, define 90. If the vectors point down, define 180
or -180. Note: I already have the var2, changing for -180 to 180.

So I want to use one color to color the vectors that almost point up
(-90 ~ 90) and use another color to color the vectors that almost
point down (-180 ~ -90, 90 ~ 180). Is there any way to do so (like
gray color areas)?

Thanks in advance.

Guangshan

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