As one of the important expressions of Regong art, Thangka has garnered increasing popularity due to its complex structure, bright colors, clear lines, and exquisite paintings. However, capturing Thangka images in dimly lit temple settings often presents challenges such as uneven illumination, high noise, color distortion, and loss of detail information. To address these issues, a semi-interactive low illumination Thangka image enhancement method based on color palettes was proposed. Firstly, based on the Retinex model, a low-illumination enhancement network, RCUNet, incorporating the convolutional block attention module (CBAM) and U-Net, was designed. Through the designed loss function, iterative training was conducted to reconstruct the illumination, reflection, and noise maps, thus synthesizing an enhanced result. For interaction, the main colors of the enhanced image were extracted and corresponding color palettes were generated using an improved K-means algorithm. Then, modifying these color palettes further improved the colors of the enhanced image. Finally, compared with several currently popular enhancement methods, quantitative and qualitative comparison experiments were undertaken on the Thangka datasets. The experimental results demonstrated that this method could yield the best results in three indicators: NIQE, PIQE, and PSNR scores.