Quarter - Semi - Whole

Let the radius of the blue circle be $r$ . Then, the radius of the yellow circle will be $2r$ and of the red circle will be $4r$ .

---

Thus, the area of the blue circle will be $\color{#3D99F6}{\boxed{πr^2}}$

---

Area of yellow region = Area of yellow semi circle - Area of blue circle $\newline$ $\frac{1}{2}π(2r)^2 - πr^2$ $\newline$ $2πr^2 - πr^2$ Thus, the area of the yellow region will be $\color{#CEBB00}{\boxed{πr^2}}$

---

Area of Red region = Area of Red quarter circle - Area of yellow semi circle $\newline$ $\frac{1}{4}π(4r)^2 - \frac{1}{2}π(2r)^2$ $\newline$ $4πr^2 - 2πr^2$ Thus, the area of the red region will be $\color{#D61F06}{\boxed{2πr^2}}$

---

Thus the ratio of the $\color{#3D99F6}{\text{Blue area}}$ : $\color{#CEBB00}{\text{Yellow area}}$ : $\color{#D61F06}{\text{Red area}}$ :: $\boxed{\color{#3D99F6}{1} : \color{#CEBB00}{1} : \color{#D61F06}{2}}$