Checking the color of the pixel in VHDL
You can represent hexadecimal literals for assignment or comparison with bit vectors of various types (like std_logic_vector) using a notation of the form x&quot;ab12&quot;. For example:
if ( r_in =x&quot;AA0000&quot; ) then
  r_out &lt;= x&quot;0000AA&quot;;
  b_out &lt;= x&quot;AA0000&quot;;
end if;

For integers, you can use a notation like 16#ab12#, reference https://stackoverflow.com/questions/38777859/vhdl-using-hex-values-in-constants