Here's a color picker that may be worth trying out: https://github.com/tossnet/Blazor-Color-Picker
There's a time picker here that allows an option for only time: https://blazor.radzen.com/datepicker
You could also build in a JavaScript based color or time picker and invoke it with JS interop. You can learn more about this approach at https://docs.microsoft.com/en-us/aspnet/core/blazor/call-javascript-from-dotnet?view=aspnetcore-3.1