Cannot change value of key in an object with TypeScript

I am unable to change the value of a key in an object with typescript. These are the types

export enum FOO_TYPES {
    red = "red",
    green = "green"
}

export type FooTypes = {
    [key in keyof typeof FOO_TYPES]: boolean
}

enum SOME_OTHER_ENUM {
    a = "abc",
    d = "def", 
    e = "ghi"
}

export interface SomeMoreData {
    id: number,
    key: SOME_OTHER_ENUM,
    priceA: number,
    priceB: number,
    red: boolean,
    green: boolean,
}

type ProjectProps = {
    [key in SOME_OTHER_ENUM]?: {
        project: SomeMoreData ,
        amountPriceAPriceB: {
            sumPriceA: number;
            sumPriceB: number;
        }
    }
}

interface GroupedProjectProps {
    [FOO_TYPES.red]: ProjectProps,
    [FOO_TYPES.green]: ProjectProps
};

Now I am having this function

const someFunc = (projects: GroupedProjectProps) => {
    const availableTypes: FooTypes = {
        red: false,
        green: false
    };

    (Object.keys(projects) as Array<keyof typeof FOO_TYPES >).map(type => {
        if (Object.keys(projects[type]).length > 0)  availableTypes[type] = true
    })
}

Which gives me the following error

Cannot assign to ‘red’ because it is a read-only property.

Cannot assign to ‘green’ because it is a read-only property.

Which I do not understand why this error is coming up…
Here is a playground

(Object.keys(projects) as Array<keyof typeof FOO_TYPES >).map(type=> {
    const a = projects[compensateType]
    if (Object.keys(a).length > 0)  availableTypes[type] = true
})
...

>Solution :

The problem lies in the fact that your FooTypes has readonly properties.

export type FooTypes = {
  [key in keyof typeof FOO_TYPES]: boolean
}

/**
type FooTypes = {
  readonly red: boolean;
  readonly green: boolean;
}
*/

See readonly modifier for properties

You can use Mapping Modifiers to make the properties mutable

export type FooTypes = {
  -readonly [key in keyof typeof FOO_TYPES]: boolean
}

/**
type FooTypes = {
  red: boolean;
  green: boolean;
}
*/

Playground