How to assign a RGB background color to a Quarto dashboard valuebox?

Consider the following quarto dashboard:

---
title: "Test"
format: dashboard
---

```{python}
#| content: valuebox
#| title: "Test Box"
dict(value=10, color="red") 
```

How can I define the background color of the valuebox dynamically using RGB colors? I am probably missing the correct syntax.

Doing it like this doesn't lead to the expected result:

---
title: "Test"
format: dashboard
---

```{python}
#| content: valuebox
#| title: "Test Box"
dict(value=10, color="background-color: rgb(255,0,0)") 
```

You can convert the rgb values to hex:

---
title: "Test"
format: dashboard
---

```{python}
#| content: valuebox
#| title: "Test Box"
dict(value=10, color='#%02x%02x%02x' % (255, 0, 0))
```