[ROOT] Workaround diagnostics when slow type lookup of literal in TColorNumber ctor param

Author: aaronj0

core/base/inc/TColor.h

@@ -147,7 +147,7 @@ class TColorNumber {
    // TColorNumber is designed to be constructed implicitly, and C++ won't do
    // two user-defined conversions in a single implicit conversion chain.
    inline TColorNumber(const char *color) : TColorNumber{std::string{color}} {}
-   TColorNumber(std::array<Float_t, 3> rgb);
+   TColorNumber(std::vector<Float_t> rgb);
    Int_t number() const { return fNumber; }
 
 private:

core/base/src/TColor.cxx

@@ -3723,4 +3723,4 @@ TColorNumber::TColorNumber(std::string const &color)
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Instantiate a color from a tuple of RGB values between 0.0 and 1.0.
-TColorNumber::TColorNumber(std::array<Float_t, 3> rgb) : fNumber{TColor::GetColor(rgb[0], rgb[1], rgb[2])} {}
+TColorNumber::TColorNumber(std::vector<Float_t> rgb) : fNumber{TColor::GetColor(rgb[0], rgb[1], rgb[2])} {}