You don't check if the player has smaller points, than 500, and if they have more than 500 you always set it to SetEntityRenderColor(i, 128, 128, 128, 255); no matter how many points they have.
try this:
PHP Code:
public Action:Timer_SetColor(Handle:timer)
{
for(new i = 1; i < MaxClients; i++)
{
if(IsClientInGame(i) && IsPlayerAlive(i))
{
if (ClientPoints[i] > 5000000)
SetEntityRenderColor(i, 0, 0, 0, 252);
else if (ClientPoints[i] > 1000000)
SetEntityRenderColor(i, 255, 0, 0, 255);
else if (ClientPoints[i] > 500000)
SetEntityRenderColor(i, 0, 0, 255, 255);
else if (ClientPoints[i] > 100000)
SetEntityRenderColor(i, 255, 255, 0, 255);
else if (ClientPoints[i] > 50000)
SetEntityRenderColor(i, 0, 255, 255, 255);
else if (ClientPoints[i] > 10000)
SetEntityRenderColor(i, 0, 255, 0, 255);
else if (ClientPoints[i] > 5000)
SetEntityRenderColor(i, 0, 128, 0, 255);
else if (ClientPoints[i] > 1000)
SetEntityRenderColor(i, 128, 128, 0, 255);
else if (ClientPoints[i] > 500)
SetEntityRenderColor(i, 128, 128, 128, 255);
else SetEntityRenderColor(i, 255, 255, 255, 255);
}
}
return Plugin_Handled;
}