## 3 Results and Discussion
The scale bar for all images is 5 \(\upmu\)m.  
Figure 2: The color pallets taken from processed (**a**) stainless steel, (**b**) copper, (**c**) aluminum, and (**d**) brass by digital camera at different viewing angles. The scanning speeds for stainless steel, copper, aluminum, and brass were 350, 400, 500, and 450 mm/s, respectively. The fluence of the laser beam was 1.0/cm\({}^{2}\). As \(\beta\) increased, colors shifted towards the longer wavelength region of the visible spectrum. The incident light angle was around 20 degrees. LIPSS could be produced by pre-structured beams [12; 16] or due to excitation of SPP waves [48], i.e. surface plasmons coupled to an incident laser pulse. In the latter case, any pre-existing structures or initial surface roughness can serve as centers for SPP excitation [49]. At these centers, normally comprising a local electronic density jump, the fast oscillating electromagnetic field can result in a local collective motion of electrons. Such SPP waves can travel across the surface with distances up to tens of microns, depending on the optical properties of the medium [50]. The optical properties of aluminum, stainless steel, brass, and copper satisfy the conditions of SPP excitation [51], which results in generation of LIPSS similar to those detected in both single-pulse [52] and multi-pulse experiments [53]. Theoretical interpretation of the SPP influence on the mechanism of metal surfaces restructuring with laser pulses was recently reported in [23]. The interference of the incident laser field with the excited SPP field may lead to laser intensity redistribution across the irradiated surface, which results in modulation of the sample surface heating  
Figure 4: Reflectance spectra from the treated surfaces [(**a**) aluminum, (**b**) stainless steel, (**c**) copper] and non-treated surfaces [(**d**) aluminum, (**e**) stainless steel, (**f**) copper]. Different curves on each graph correspond to different angles of observation. One can see that, in the case of non-treated surfaces, the reflectance spectra remain the same at different angles of observation, contrary to the case of treated surfaces. The colors in (**a–c**) correspond to the colors viewable by eye at the corresponding angles. The angle (\(\beta\)) ranged from 0\({}^{\circ}\) to 40\({}^{\circ}\), where 0\({}^{\circ}\) corresponds to the position of the spectrometer when it is perpendicular to the sample. As \(\beta\) increased, longer wavelengths were detected. and hence the growth of periodic patterns [21]. Moreover, the laser intensity redistribution across the surface can induce the growth of the periodic nanostructures even though the averaged incident fluence is below the melting threshold. In addition, it was theoretically identified that due to the correlation established between the laser intensity redistribution and the pre-structured surface, the formation of LIPSS becomes more preferable in the multi-pulse regime [54]. The latter was confirmed in recent experimental studies on Si [55]. Our experiments were carried out in the multi-pulse regime, when the range of overlaps between nearby beams was adjusted by the scan speed, while maintaining suitable average power and fluence of the heating pulses. Thus, application of high pulse repetition laser-matter interactions can be considered an advanced approach for simultaneous modifications of coloring and wettability properties of the processed surfaces. Besides showing the ability to produce new colors on the pristine samples, below we demonstrate that the color on the surface of processed metals can be erased and re-colored by using the same laser radiation. As shown in Figure 5, a sample of aluminum was made dark golden (A) and then erased to restore it to almost its original color. The same sample was then colored to a whitish color (B), part of which was erased again, and colored to the black semi-circle (C).