The value set to the last spin editor is overridden with its previous value. 

How to reproduce: check the attached videos

Workaround: 
 public partial class Form1 : Form
 {
     public Form1()
     {
         InitializeComponent();

         this.radColorBox1.ValueChanging += radColorBox1_ValueChanging;
         ((RadForm)this.radColorBox1.ColorBoxElement.ColorDialog.ColorDialogForm).FormClosing += Form1_FormClosing;
     }

     bool cancelValueChange;
     Telerik.WinControls.UI.RadColorPicker.ProfessionalColors professionalColors;
     private void Form1_FormClosing(object sender, FormClosingEventArgs e)
     {
         Control colorSelector = this.radColorBox1.ColorBoxElement.ColorDialog.ColorDialogForm.RadColorSelector;
         RadPageView pageView = colorSelector.Controls[3] as RadPageView;
         if (pageView.SelectedPage.TabIndex == 3)
         {
             cancelValueChange = true;
             professionalColors = pageView.Pages[3].Controls[0] as Telerik.WinControls.UI.RadColorPicker.ProfessionalColors;
         }
         else
         {
             professionalColors = null;
         }
     }

     private void radColorBox1_ValueChanging(object sender, Telerik.WinControls.UI.ValueChangingEventArgs e)
     {
         if (cancelValueChange && professionalColors != null) 
         {
             e.Cancel = true;

             RadSpinEditor alphaSpinEditor = professionalColors.Controls[12] as RadSpinEditor;
             RadSpinEditor redSpinEditor = professionalColors.Controls[15] as RadSpinEditor;
             RadSpinEditor greenSpinEditor = professionalColors.Controls[11] as RadSpinEditor;
             RadSpinEditor blueSpinEditor = professionalColors.Controls[7] as RadSpinEditor;
             cancelValueChange = false;

             this.radColorBox1.Value = Color.FromArgb((int)alphaSpinEditor.Value, (int)redSpinEditor.Value, (int)greenSpinEditor.Value, (int)blueSpinEditor.Value);
             
         }
     }
 }