\documentclass[transparent]{standalone}
\usepackage[x11names]{xcolor} % Uso del paquete xcolor con la opción x11names
\usepackage{tikz,siunitx}
\usepackage[spanish]{babel}
\usepackage[utf8]{inputenc}

\usepackage[T1]{fontenc}

\def\luma{2.75} % Variable de intensidad de la portadora de luma
\def\chroma{2.75} % Variable de intensidad de la portadora de chroma
\def\audio{2.5} % Variable de intensidad de la portadora de audio
\usepgflibrary{arrows.meta} % Uso de bibloteca de flechas
\begin{document}
\begin{tikzpicture}[scale=2]
        % Estilo de nodo para colocar en las líneas de color Magenta1
        \tikzstyle{ann} = [fill=white,font=\normalsize,inner sep=1pt]
	% Ejes del gráfico
	\draw [very thick,Blue2,-Stealth] (0,0)--(8,0) node [right]{$f(\si{\MHz})$}; % Frecuencias
	\draw [very thick,Blue2,-Stealth] (0,0)--(0,3) node [above]{$\si{\dB}$}; % Intensidad 
	% Ticks
	 \foreach  \x in {0,...,8}
     	\draw (\x,1pt) -- (\x,-3pt);
    	% Indicadores de frecuencias
    	\draw [very thin,black] (0,0)--(0,-1);
	\draw [very thin,black] (1.25,0)--(1.25,-0.75);
	\draw [very thin,black] (5.5,0)--(5.5,-0.25);
	\draw [very thin,black] (5.65,0)--(5.65,-0.5);
	\draw [very thin,black] (7.75,0)--(7.75,-0.75);
	\draw [very thin,black] (8,0)--(8,-1);
	% Espectros 
	\draw [very thick,SteelBlue2,fill=Thistle1] (0,0)--(0.625,2.5)--(7,2.5)--(7.25,0)--cycle;   % Luminancia 
	\draw [very thick,SteelBlue2,fill=Ivory1] (4.5,0)--(4.625,1.5)--(7.1,1.5)--(7.25,0)--cycle; % Crominancia
	\draw [very thick,SteelBlue2,fill=PaleGreen1] (7.65,0)--(7.7,\audio)--(7.8,\audio)--(7.85,0)--cycle; % Audio
	% Portadoras
	 \draw [very thick,Red1] (1.25,0)--(1.25,\luma) node [above,black,align=center]{Portadora\\de luma}; % Luminancia
	\draw [very thick,Red1] (5.5,0)--(5.5,\chroma);% Crominancia 1
	\draw [very thick,Red1] (5.65,0)--(5.65,\chroma) node[above,black,align=center] {Portadoras\\de crominancia};% Crominancia 2
	\draw [very thick,Red1] (7.75,0)--(7.75,\chroma) node[above,black,align=center] {Portadora\\de audio};% Audio
	% Lineas de color Magenta1
   	 \draw [very thick,Magenta1,Stealth-Stealth] (0,-0.25)--(1.25,-0.25); % Orígen - Portadora de Luminancia
	\draw [very thick,Magenta1,Stealth-Stealth] (1.25,-0.25)--(5.5,-0.25); % Portadora de Luminancia - Portadora de Crominancia 1
	\draw [very thick,Magenta1,Stealth-Stealth] (1.25,-0.5)--(5.65,-0.5); % Portadora de Luminancia - Portadora de Crominancia 2
	\draw [very thick,Magenta1,Stealth-Stealth] (1.25,-0.75)--(7.75,-0.75); % Portadora de Luma - Portadora de Audio
	\draw [very thick,Magenta1,Stealth-Stealth] (0,-1)--(8,-1) ; % Ancho de banda total
	% Nodos con los anchos de banda
	\node[ann] at (0.65,-0.25){$ 1.25 \, \si{\MHz}$}; 
	\node[ann] at (3.5,-0.25){$ 4.25 \, \si{\MHz}$}; 
	\node[ann] at (3.5,-0.5){$ 4.4 \, \si{\MHz}$};
	\node[ann] at (4,-0.75){$ 6.5 \, \si{\MHz}$}; 
	\node[ann] at (4,-1){$ 8 \, \si{\MHz}$}; % Origen hasta el ancho de banda total
  
\end{tikzpicture}

\end{document}