Don't use red when backend is explicitly disabled

These messages stand out, but they really shouldn't because there is
nothing unexpected in the fact that an explicitly disabled backend is
not used, so use a more subdued colour for them.

cmake/SociBackend.cmake

@@ -230,7 +230,7 @@ macro(soci_backend NAME)
       endif()
 
     else()
-        colormsg(HIRED "${NAME}" RED "backend disabled, since")
+        colormsg(YELLOW "${NAME} backend explicitly disabled")
     endif()
 
   endif()

cmake/SociDependencies.cmake

@@ -91,7 +91,7 @@ foreach(external ${SOCI_ALL_DEPENDENCIES})
     include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/dependencies/${external}.cmake)
   else()
     set(${EXTERNAL}_FOUND FALSE CACHE BOOL "${external} found" FORCE)
-    colormsg(HIRED "${external}:" RED "disabled, since ${disabled_var}_${EXTERNAL}=OFF")
+    colormsg(HICYAN "${external}:" YELLOW "disabled, since ${disabled_var}_${EXTERNAL}=OFF")
     unset(disabled_var)
   endif()