A Composable function designed to showcase all the colors of a Material theme, in both light and dark modes.

MaterialColorsPreview.kt

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.material3.ColorScheme
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.luminance
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp

@Composable
fun MaterialColorsPreview(
    darkColorScheme: ColorScheme,
    lightColorScheme: ColorScheme,
    modifier: Modifier = Modifier,
) {
    Column(modifier = modifier) {
        Row(
            modifier = Modifier.fillMaxWidth(),
            horizontalArrangement = Arrangement.End
        ) {
            Text(
                modifier = Modifier
                    .padding(horizontal = 8.dp)
                    .width(56.dp),
                text = "Dark",
                textAlign = TextAlign.Center
            )

            Text(
                modifier = Modifier
                    .padding(horizontal = 8.dp)
                    .width(56.dp),
                text = "Light",
                textAlign = TextAlign.Center
            )
        }
        LazyColumn(modifier = Modifier.fillMaxSize()) {
            item { ColorRow("primary", darkColorScheme.primary, lightColorScheme.primary) }
            item { ColorRow("onPrimary", darkColorScheme.onPrimary, lightColorScheme.onPrimary) }
            item { ColorRow("primaryContainer", darkColorScheme.primaryContainer, lightColorScheme.primaryContainer) }
            item { ColorRow("onPrimaryContainer", darkColorScheme.onPrimaryContainer, lightColorScheme.onPrimaryContainer) }
            item { ColorRow("inversePrimary", darkColorScheme.inversePrimary, lightColorScheme.inversePrimary) }
            item { ColorRow("secondary", darkColorScheme.secondary, lightColorScheme.secondary) }
            item { ColorRow("onSecondary", darkColorScheme.onSecondary, lightColorScheme.onSecondary) }
            item { ColorRow("secondaryContainer", darkColorScheme.secondaryContainer, lightColorScheme.secondaryContainer) }
            item { ColorRow("onSecondaryContainer", darkColorScheme.onSecondaryContainer, lightColorScheme.onSecondaryContainer) }
            item { ColorRow("tertiary", darkColorScheme.tertiary, lightColorScheme.tertiary) }
            item { ColorRow("onTertiary", darkColorScheme.onTertiary, lightColorScheme.onTertiary) }
            item { ColorRow("tertiaryContainer", darkColorScheme.tertiaryContainer, lightColorScheme.tertiaryContainer) }
            item { ColorRow("onTertiaryContainer", darkColorScheme.onTertiaryContainer, lightColorScheme.onTertiaryContainer) }
            item { ColorRow("background", darkColorScheme.background, lightColorScheme.background) }
            item { ColorRow("onBackground", darkColorScheme.onBackground, lightColorScheme.onBackground) }
            item { ColorRow("surface", darkColorScheme.surface, lightColorScheme.surface) }
            item { ColorRow("onSurface", darkColorScheme.onSurface, lightColorScheme.onSurface) }
            item { ColorRow("surfaceVariant", darkColorScheme.surfaceVariant, lightColorScheme.surfaceVariant) }
            item { ColorRow("onSurfaceVariant", darkColorScheme.onSurfaceVariant, lightColorScheme.onSurfaceVariant) }
            item { ColorRow("surfaceTint", darkColorScheme.surfaceTint, lightColorScheme.surfaceTint) }
            item { ColorRow("inverseSurface", darkColorScheme.inverseSurface, lightColorScheme.inverseSurface) }
            item { ColorRow("inverseOnSurface", darkColorScheme.inverseOnSurface, lightColorScheme.inverseOnSurface) }
            item { ColorRow("error", darkColorScheme.error, lightColorScheme.error) }
            item { ColorRow("onError", darkColorScheme.onError, lightColorScheme.onError) }
            item { ColorRow("errorContainer", darkColorScheme.errorContainer, lightColorScheme.errorContainer) }
            item { ColorRow("onErrorContainer", darkColorScheme.onErrorContainer, lightColorScheme.onErrorContainer) }
            item { ColorRow("outline", darkColorScheme.outline, lightColorScheme.outline) }
            item { ColorRow("outlineVariant", darkColorScheme.outlineVariant, lightColorScheme.outlineVariant) }
            item { ColorRow("scrim", darkColorScheme.scrim, lightColorScheme.scrim) }
            item { ColorRow("surfaceBright", darkColorScheme.surfaceBright, lightColorScheme.surfaceBright) }
            item { ColorRow("surfaceDim", darkColorScheme.surfaceDim, lightColorScheme.surfaceDim) }
            item { ColorRow("surfaceContainer", darkColorScheme.surfaceContainer, lightColorScheme.surfaceContainer) }
            item { ColorRow("surfaceContainerHigh", darkColorScheme.surfaceContainerHigh, lightColorScheme.surfaceContainerHigh) }
            item { ColorRow("surfaceContainerHighest", darkColorScheme.surfaceContainerHighest, lightColorScheme.surfaceContainerHighest) }
            item { ColorRow("surfaceContainerLow", darkColorScheme.surfaceContainerLow, lightColorScheme.surfaceContainerLow) }
            item { ColorRow("surfaceContainerLowest", darkColorScheme.surfaceContainerLowest, lightColorScheme.surfaceContainerLowest) }
        }
    }
}

@Composable
private fun ColorRow(name: String, darkColor: Color, lightColor: Color) {
    Row(
        modifier = Modifier
            .fillMaxWidth()
            .padding(vertical = 2.dp),
        verticalAlignment = Alignment.CenterVertically
    ) {
        Text(
            modifier = Modifier.weight(1f),
            text = name,
            textAlign = TextAlign.End,
            fontSize = 13.sp
        )

        Text(
            modifier = Modifier
                .padding(horizontal = 8.dp)
                .width(56.dp)
                .height(32.dp)
                .background(darkColor),
            text = darkColor.toShortString(),
            textAlign = TextAlign.Center,
            fontSize = 12.sp,
            color = if (darkColor.luminance() > 0.5) Color.Black else Color.White,
        )

        Text(
            modifier = Modifier
                .padding(horizontal = 8.dp)
                .width(56.dp)
                .height(32.dp)
                .background(lightColor),
            text = lightColor.toShortString(),
            textAlign = TextAlign.Center,
            fontSize = 12.sp,
            color = if (lightColor.luminance() > 0.5) Color.Black else Color.White,
        )
    }
}

private fun Color.toShortString(): String {
    val a = if (alpha != 1f) (alpha * 0xff).toInt().toString(16).padStart(2, '0') else ""
    val r = (red * 0xff).toInt().toString(16).padStart(2, '0')
    val g = (green * 0xff).toInt().toString(16).padStart(2, '0')
    val b = (blue * 0xff).toInt().toString(16).padStart(2, '0')
    return "$a$r$g$b"
}