Read the user's OS accent colour and high-contrast setting as reactive Compose state.

The system-color module reads the user's OS accent colour and high-contrast setting from Kotlin. Both are exposed as reactive Compose state that recomposes when the user changes them in system settings, so you can feed the accent straight into a Compose color scheme. Supported on macOS, Windows, and Linux.

Add the dependency

build.gradle.kts

dependencies {
    implementation("dev.nucleusframework:nucleus.system-color:2.0.7")
}

Read the system accent colour

Call systemAccentColor() inside a composable. It returns a Color? and recomposes whenever the user picks a different accent. Fall back to your own palette when it returns null:

import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.darkColorScheme
import androidx.compose.runtime.Composable
import dev.nucleusframework.systemcolor.systemAccentColor

@Composable
fun App() {
    val accent = systemAccentColor()

    val scheme = when {
        accent != null -> darkColorScheme(primary = accent)
        else -> darkColorScheme()
    }

    MaterialTheme(colorScheme = scheme) {
        // The UI recomposes when the accent colour changes.
    }
}

Read the high-contrast setting the same way with isSystemInHighContrast():

import androidx.compose.runtime.Composable
import dev.nucleusframework.systemcolor.isSystemInHighContrast

@Composable
fun AppContent() {
    val highContrast = isSystemInHighContrast()
    // Adjust borders, elevation, or contrast tokens when highContrast is true.
}

How it works

On each supported platform, a native JNI bridge starts observing the OS accent-colour and contrast change notifications and forwards them to registered listeners.

systemAccentColor() and isSystemInHighContrast() subscribe to that bridge and hold the current value in Compose state. Any composable that reads them recomposes when the value changes, so there is no polling and no manual refresh.

systemAccentColor() returns null when the platform cannot supply an accent colour. That includes any platform other than macOS, Windows, or Linux. Treat null as "use your own brand colour".

Not every OS or configuration exposes an accent colour. Always handle the null case and fall back to your own palette.

API reference

Check platform support

fun isSystemAccentColorSupported(): Boolean

Returns true when the current platform can report an accent colour. This is a plain function, not a composable, so you can call it outside composition — for example, to enable or disable a settings toggle.

Read the accent colour

@Composable
fun systemAccentColor(): Color?

Returns the current accent colour, or null when the platform does not support it. Recomposes when the accent changes.

Read the high-contrast flag

@Composable
fun isSystemInHighContrast(): Boolean

Returns true when the OS is in high-contrast mode. Recomposes when the user toggles the accessibility contrast setting.

What's next

Dark mode detection — pair with the accent colour to derive a full OS-driven theme.
System info — read the OS, hardware, and battery details from Kotlin.
OS integration — the rest of the native platform modules.

System accent colour